5 egg whites
190gm caster sugar
310gm unsalted butter
2tsp vanilla extract
Cut the butter into 2cm cubes and leave out of the fridge whilst working on the rest of the recipe. You want the butter slightly softened but still cold so you don’t end up with a soupy mess.
Place the egg whites and sugar in the bowl of your stand mixer and whisk together.
Place the bowl over a saucepan of boiling water and whisk constantly until the egg mixture reaches 70-75°C (or 160°F).
Remove from the heat and, using the whisk attachment of the mixer, whisk on high speed until the outside of the bowl cools to room temperature and the mixture is white and fluffy (about 10-15 minutes).
Switch over to the paddle attachment and, on medium speed, beat in the butter one cube at a time. This is where patience comes in. Don’t be tempted to add it all in too quickly.
Once all the butter has been added, turn up to high speed and keep beating until the frosting is light and fluffy and no pieces of butter are visible. Note that during this process your meringue will deflate and may even look curdled or soupy. Don’t fret, just keep mixing and it will eventually come together again. This may take 10 minutes or so.
If you want a vanilla frosting, add it in at this point and beat to combine.
If you are colouring your frosting this is also the point to add it.
Your buttercream is ready to go!
If you want to make it ahead of time, it can be stored in an airtight container in the fridge for 1 week. When you are ready to use it, allow it to come to room temperature and then beat it again until it returns to its light, fluffy state.
Some alternate flavouring ideas which can be added at the point where the vanilla was added above: Chocolate : melt 100gm of good quality dark chocolate and beat into frosting mix until incorporated. Caramel : add ¼ cup of dulce de leche or caramel sauce to the frosting and beat to incorporate. For a salted variety, add ¼ tsp flaked sea salt also.
Citrus : add 2tbs of lemon or lime curd to the frosting mix and beat to incorporate.
Nutella : add 100gm of Nutella to the frosting mix and beat to incorporate.
Berry : add ¼ cup of berry puree to the frosting and mix to incorporate. If making your own puree, pass through a fine sieve before adding to remove any seeds or lumps. Raspberries and strawberries work well with this and can be added with the vanilla also.