Buttercream cupcakes

Tips for Extreme Weather Cake Decorators: Fillings & Frostings

If you spend hours and hours decorating a beautiful cake, it can be devastating if extreme weather conditions are out to destroy all your hard work so I am passing on some tips that may help you.

For the majority of my cake making and decorating career, I lived in England where it seldom gets very hot or too cold, and I never noticed if it was humid or not. However, since moving to central Europe several years ago, where it can drop to -15C/5F in the winter and rise to over 40C/104F in the summer and the humidity can fluctuate, I am now experiencing some of the issues that are everyday problems for many people.

Since living here I have used fillings and frosting, in the summer, that should withstand heat and humidity. However, I have found that venues seem to be well prepared for most weather conditions so I can honestly say that I have not been able to test them properly.

That was until…


Last year I made a two-tiered cake as a gift for a friend for a birthday celebration in August that I was also to attend. When August came around we were in the middle of an extreme heat wave so I knew that I had to choose fillings and icing that would be less likely to melt.

Because it was left up to me to choose how to present the cakes, I chose to use a cake stand that displayed the cakes individually rather than stack them because the weight of a heavy cake resting on another cake, that is filled with buttercream or something similar, can be a recipe for disaster.

I also used three dowels in each cake so there would be no chance of the layers slipping. It may have been overkill, especially as the cakes were not stacked, but as I was going to be at the party, I wanted to be as sure as I could that I was not going to be judged on a crooked cake.

By the time it came to set off I was becoming paranoid, and I had visions of it melting on the way, so I packed each tier in separately, with plenty of ice in the bottom of each box and I even took a fan with me in case the venue wasn’t air conditioned properly.

Upon arrival, before I unloaded the cake, I was taken to where it was to be displayed and to my horror the party was to be held in a garden, and the cake was to be put on a table in direct sunlight, outside. Admittedly, it was 5 pm, but it was still nearly +30 C, and there was also some humidity.

Secretly I was panicking. Should I make a fuss in front of all the people standing around waiting for me to put out the cake and demand an air-conditioned place to put it or should I just pretend everything was OK?

 I may have been wrong, but I decided just to go ahead and put it where they wanted it so I carried on as if everything was just as it should be, set the cake up, walked away and joined in the party and what a great party it was.

I tried not to look at the cake during the evening and just kept my fingers crossed that I had chosen the right fillings etc., that wouldn’t melt and that my creation wouldn’t ruin the party.

I held my breath and cut the cake…


Three hours later I was asked to cut the cakes. I could feel myself panicking again. It didn’t look as if it had moved but what was I going to do if the inside of the cake was a big melted mess.

The guests gathered around to watch me cut the cakes, and you cannot imagine the relief when I cut into them, and they were just perfect.

The bottom tier was a 28cm /11”,  three-layered vanilla sponge filled with homemade lemon curd and ermine lemon buttercream, crumb coated in ermine buttercream and covered in lemon flavored rolled fondant.

The top tier was a 20cm/8” dark chocolate, three-layered cake, filled with dark chocolate whipped ganache, crumb coated with unwhipped dark chocolate ganache and covered with rolled fondant.

I had never used Ermine buttercream before and to tell you the truth when a friend suggested I use it; I did not like the sound of it. Some people call it flour buttercream or cooked milk buttercream and I didn’t see how that would be nice in a cake, but I was assured by the friend who gave me the recipe that it was really good and stable in heat and humidity.

I did a test batch the week before I need it for the cake and I was amazed at the result. It was the creamiest, smoothest buttercream I had ever tasted. Absolutely so hint of flour, and I have been using it ever since, even through the winter, because it is so good and everyone likes it, and it did live up to its reputation of being stable in heat and humidity.

I used lactose-free butter and lactose-free milk in my ermine buttercream because I am intolerant to lactose and so were several of the party guests and it worked perfectly.

Ermine Buttercream



30g1½ ozCornflour/cornstarch
30g1½ ozAll-purpose Flour
300g10½ ozGranulated Sugar
355 ml1.5 cups/12 fl ozMilk
¼ tsp Salt
½ tsp Vanilla or lemon extract (or to own taste)
340g Butter – soft but not melted


  1. You will need a medium-sized saucepan and a bowl that is bigger than the pan.
  2. Put some cold water in the bowl and set to one side. This is used to begin the cooling process once the mixture is cooked.
  3. In a bowl combine the cornflour/cornstarch, flour, milk, and salt. Stir until all are smoothly mixed together.
  4. Pour the mixture through a fine sieve into the pan then add the sugar.
  5. Cook the mixture over medium heat, constantly stirring, until it thickens and comes to the boil then turn the heat right down, and still stirring, simmer for 2 minutes.
  6. Take the pan off the heat and place in the bowl of cold water, making sure not to get any of the water into the mixture in the pan, keep gently stirring for two minutes.
  7. Remove the pan from the bowl of water and wipe the bottom dry.
  8. Empty the contents of the pan into a stand mixer bowl or a bowl you will use with a hand mixer.
  9. Place a piece of cling film/plastic wrap directly onto the mixture in the bowl making sure there is no space for air to get to it.
  10. Leave until the mixture has dropped to room temperature.
  11. Once the mixture has reached room temperature, add the vanilla or lemon extract and whisk slowly until combined.
  12. Add the soft butter a spoonful at a time, slowly whisking between additions, until it has all been added.
  13. Turn the mixer up to medium speed and whisk for 5 mins until the buttercream is light and fluffy.
  14. Cover and leave to stand at room temperature for about 1 hour to thicken.

For chocolate flavored ermine buttercream add three tablespoons unsweetened, cocoa powder to the milk mixture, at the start of the process, and leave out the vanilla or lemon extract


Chocolate Ganache is so good…


If you are a chocoholic, like I am, and dark chocolate is your favorite, then there’s nothing better than a dark chocolate cake filled with dark chocolate whipped ganache and covered with dark, unwhipped chocolate ganache.

My experience of ganache staying stable in the heat may have been because it was covered with rolling fondant. However, chocolate ganache made with high-quality dark chocolate (75%-80% cocoa) should be stable up to 85F/30C so my cake may have been just within the melting point.

If you are going to make chocolate ganache for decorating a cake that will be in a hot/humid situation then using white chocolate is not a good idea. White chocolate is a by-product of the chocolate making process and is made using cocoa butter, milk, sugar, and some flavoring so it is more like a candy.

Milk chocolate can have as little as 10% cocoa and is mixed with milk and other ingredients, so that doesn’t stand up very well in the heat either.

Whipped or not whipped…


Whipped ganache can be used for filling a cake, covering a cake and for piping. Ganache that has not been whipped is used as a frosting to coat a cake, as a filling between layers and for crumb coating a cake,

The proportions of chocolate and cream used for ganache are based on weight and for my cake that got left in the sun, I used a 2-1 ratio which means I had double the weight of chocolate to cream e.g 227g/8 oz chocolate to 114g/ 4 oz cream.

Under normal circumstances (not so much heat/humidity) I would use a 1:1 ratio – equal parts chocolate and cream – and that makes a softer ganache.

Chocolate Ganache



heavy/double cream  (or 30% fat lactose-free cream)

75 – 80% good quality plain chocolate

The quantities in the table below will be enough for filling for a three layer cake and a crumb coat or a filling for a two layer cake and an all-over frosting coat


Round Cake


Square Cake

SizeDark ChocolateHeavy/Double Cream  Dark ChocolateHeavy/Double Cream
6”/15cm350g/12oz175ml/6 fl oz 450g/16oz225ml/8 fl oz
7”/18cm450g/16oz225ml/8 fl oz 575g/20oz288ml/10 fl oz
8”/20cm575g/20oz288ml/10 fl oz 700g/24oz350ml/12 fl oz
9”/22.5cm650g/23oz325ml/11 fl oz 825g/28oz412ml/14  fl oz
10”/26cm775g/27oz388ml/13.5 fl oz 975g/34oz488ml/17 fl oz
11”/28cm900g/31oz450ml/15.5 fl oz 1130g/40oz565ml/20 fl oz
12”/30cm1025g/36oz512ml/18 fl oz 1325g/46oz676ml/23 fl oz

Note: Use a pan that is larger than your gas or electric ring so you don’t scorch the cream.


  1. Break the chocolate into small pieces and place in a bowl
  2. Put the cream into a pan and, on a medium, heat bring it to just below boiling point
  3. Pour the cream over the chocolate and leave for a few minutes until the chocolate has  melted
  4. Stir the mixture
  5. It may look as if it won’t combine properly at first but keep stirring and it will blend together
  6. Taste the mixture and if it is not sweet enough add some icing/confectioners sugar a teaspoon at a time and make sure it has melted. Very little sugar will sweeten the mixture so don’t add too much, or you will ruin the consistency of the ganache.
  7. Leave to cool

To spread ganache over a cake it needs to be still slightly warm to be able to pour it but thick enough to stay on the cake.

If you are going to whip the ganache, let it cool until thick then beat until light and fluffy about 2-3 mins, but be careful not to overbeat.

Another buttercream…


This buttercream also holds up quite well in humid/hot weather conditions.

Swiss/Mousseline Buttercream


All ingredients need to be at room temperature

Use a sugar thermometer to measure the temperature of the sugar syrup


454g16ozButter – soft but not melted
5 large Egg whites
200g7ozGranulated sugar
½ tsp Cream of Tartar
¼ cup  Water
½ tsp  Vanilla extract


  1. Whisk the butter until smooth and creamy
  2. Place 150g/4½oz sugar and ¼ cup water in a saucepan that is wider than the burner
  3. Heat mixture, whilst stirring,  until sugar has melted (brushing the crystals of sugar down the inside of the pan with a brush dipped in cold water).
  4. Once melted stop stirring & remove from heat and set aside
  5. Put some cold water in a bowl that is bigger than the bottom of the saucepan and set aside.
  6. Place the egg whites and the cream of tartar in the bowl of a stand mixer and using a whisk attachment, whisk until soft peak stage.
  7. Stir in the remaining sugar then whisk until the stiff peak stage is reached.
  8. Return the pan with the syrup to the heat and boil until it reaches 120C/248F on the sugar thermometer which is the softball toffee stage.
  9. Plunge the bottom of the pan into the bowl of cold water to stop the cooking process.
  10. Make sure you don’t get any water into the toffee.
  11. Leave in the water for 1 minute.
  12. With the mixer running on high speed slowly pour the toffee, in a thin stream, onto the egg whites. Be careful not to let the stream of toffee touch the mixer blade or you will have lumps of toffee in your buttercream.
  13. Once all the toffee has been incorporated into the egg whites, lower the speed of the mixer to medium and beat until the bowl feels cool.
  14. Beat in the butter, 1 spoonful at a time (it may seem thinner at first but will thicken by the time it is all added)

This buttercream will keep for up to 5 days, covered, in the fridge or it can be frozen.

Before use bring to room temperature and re-beat.

The trick is to test it…


There is no guarantee that these fillings and frosting will stand up to your particular climate and I can only emphasize the fact that you must try them out before you either make a cake for a special occasion or make a cake to sell.

Don’t try them out on a dummy cake because the cake itself will contribute to the stability of toppings or fillings.

Testing your product takes a bit of effort, but it will save a lot of disappointment.

Gum paste flowers and rolling fondant…


In my blog post about making Gum Paste Sugar Flowers, in extreme weather conditions, you will find lots of tips and information that I am sure you will find useful.

Also, in my blog post about using Rolling Fondant, in extreme weather conditions, you will find lots of tips and information that I am sure you will find useful.

If you have any tried and tested recipes, you know will stand up to extreme weather conditions, please share them as I am always ready to learn.

Joyce Freeman

Joyce Freeman



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