I love this stuff. I'm glad I persevered with it after my first few attempts. It's a frosting I wasn't overly familiar with but thought it sounded divine. Now I rarely use anything else.
There are a few different forms but they ultimately produce the same thing. There is Italian meringue buttercream, which is where you make a sugar syrup and slowly pour it into your whisking egg whites before adding cubed butter (cue sugar syrup sticking to baloon whisk, forming sugar lumps in my egg whites).
Swiss meringue buttercream on the other hand, is made by whisking egg whites and sugar over heat, before adding cubed butter.
I've found Swiss meringue buttercream gives far better results, but feel free to experiment!
3 tbsp flavour of your choice (compote, nutella, hazelnut praline paste, lemon juice etc.)
Ensure your butter is room temperature. Take it out of the fridge the day before you make this or put it in the microwave for 10 secs at a time. It should be really soft but still holding together.
Take the egg whites out of the fridge about 20 mins before you want to use them.
Weigh the egg whites and caster sugar in a heat proof bowl (or the jug of your freestanding mixer) and place over a saucepan of water. Make sure the water isn’t touching the bottom of the bowl. Put the candy thermometer into the mixture.
Whisk the mixture until it reaches approx. 70°c or if you don’t have one, for about 15 mins.
It'll start to get thicker like this...
Take the bowl off the heat and continue to whisk on a high speed until the bowl feels room temperature and no longer warm. I usually set the oven timer to 15 mins and leave it to whisk in my Kitchen Aid.
When it no longer feels warm, give the sides a good scrape down with a sputula and add the vanilla extract.
Look how thick it is now...
Switch to the paddle attachment or beaters if you’re using a hand held mixer. I often forget to do this so if you're wondering why it's staying runny, change the the PADDLE ATTACHMENT.
Reducing the speed to medium, begin to add your butter in cubes. Be patient here and make sure each cube is incorporated before adding the next.
The texture instantly changed with the paddle attachment and goes really glossy
Keep adding butter slowly, turn the speed to medium if you get impatient. I have added about two thirds of the butter at this point...
When you get to about your last three cubes of butter, you'll notice the texture change completely. You'll be able to hear the difference as the frosting starts to sound like it's slapping against the sides of the bowl
Keep going and add the remaining butter and continue to beat for another minute or so
The buttercream should be thick and holding together.
When it's all incorporated, add your compote, paste or extract and beat again to combine
I've kept mine as plain vanilla here
Mine turned out really well here but it often needs a little help... If it’s too loose, pop it in the fridge for 15 mins and re-mix. If it looks slightly split and not completely smooth, it's usually because the butter was too cold. Just put the bowl back on the pan of water and mix with a spatula until the sides just start to loosen. Then re-beat. It should be smooth and shiny and thick enough to hold together as buttercream would.
This can be stored in the fridge for up to a week. Just bring it back to room temperature and re-beat when you need it.