This is the only buttercream I'll use on my professional cakes, it looks incredibly smooth and holds it shape so well. It's very easy to work with and quite forgiveable if you bump it or make a mistake.
There can be points during the process where you think it's not going to work out, but fear not, there is always a way to fix it, so never throw it out! I have given all my tips in the recipe. I know it can be hard to follow directions, but if ever there was a time where you should follow the recipe TO THE LETTER, that time would be now. Can you handle it?
If there is one thing I have learned in my many times in making this - it cannot be rushed. You must be patient and allow the steps to complete, or you'll be wondering why "it doesn't look like the picture" trust me and trust the process, it takes time.
NB: For all of my recipes I try to make them as achievable as possible with minimal equipment, however I just don't recommend this recipe if you don't have a stand mixer, no one wants to be holding their electric beaters for 15 minutes.
Swiss Meringue Buttercream
6 egg whites (size 7 eggs)
450g caster sugar
600g butter, at room temperature, diced 1cm
Yes you're reading it right and yes its a lot of butter, but there's never been a time I've regretted making too much buttercream, only too little. And being that this is a little bit more of a faff than regular 'ol buttercream, I prefer to make a big batch in one go. This will do the crumb coat and top coat of an 8inch/22cm cake, no problem.
Place egg whites and sugar in the bowl of your stand mixer. Place over a pot of boiling water and whisk continuously until the sugar is dissolved, it will take 5-10 minutes, (test it by rubbing some between your finger and thumb to see if any sugar granules remain). If you are making this cake for a baby shower or someone who is pregnant, you will need to ensure the egg whites reach 65°C - use a candy thermometer to check this.
Transfer the bowl to your stand mixer with a whisk attachment and whip until a stiff-peak meringue forms. When you touch the side of the bowl, it should feel room temperature, if it feels warm, continue whipping until cool, before adding the butter. Add the room temperature butter (this is very important! don't use cold butter!), 1 cube at a time, on medium speed, until it's all incorporated. It may start to look watery or curdled, never fear just keep going, keep beating, it will come together.
Switch to your paddle attachment and whip on low speed for 15 minutes - yes I'm serious, set a timer. When you come back you should have a beautiful, soft, smooth, white buttercream. Now is when you can add any food colouring or flavours and beat them in.
C'est fini! Well done! Go forth and use it on all your cakes. It pipes beautifully but also just using the back of a spoon can make a stunning design too, as in my image above.
TROUBLESHOOTING:
Made too much? Put the leftover buttercream in a container in the freezer for up to a month. Allow it to come back to room temperature and then you will need to beat again before using.
Buttercream looks curdled? It's highly likely your butter was too cold. No problem we can fix it. Take out 1/2 cup of your buttercream and put it in a heat-proof container. Microwave it for about 30 seconds, until it becomes a liquid. Pour this back into your buttercream, and continue beating. This should help the mixture warm up and come together again.
Buttercream looks soupy? Maybe it's super hot where you are or maybe your butter was a bit too warm/oily. No worries - place the whole bowl of buttercream in the fridge for about 10 minutes, and then try whipping again. Repeat the process until it has cooled down enough and whips up nicely.