I am going to let you on a little secret: I only recently started using Swiss meringue buttercream - or SMBC as they say! Indeed, before that, I used "Fondant" as a base for my buttercream! Not the roll-out fondant, no, no. The "Patissier Fondant", the thick white sugar syrup we use to cover Eclairs and Mille-Feuilles in pâtisserie. I must say, I have been quite happy with it so far as the result was a slightly whipped, and very smooth buttercream. It was definitely more work than the "American Buttercream" but really worth the extra effort. My main concern always being to use less sugar, my fondant recipe is based on a 0.8/1 fondant/butter ratio.
Last time I actually made a Swiss Meringue buttercream was about 9 years ago, during my patisserie training (I know right?!)! But in the past few weeks, I had in mind to find a lighter option for my cakes filling, so I went through my old recipes and found a few new ones online. After some trials (I tested about four different recipes), and a few tweaks to make it really to my taste, I am at last happy to share with you the recipe I came up with.
Before we dive in
I want to insist on a thing: Swiss Meringue Buttercream CAN be tricky, but if you master your temperatures, it doesn't have to be! I know some people actually told me they were avoiding it because is it too complicated, but in reality, like many things in pâtisserie, it is a question of chemistry. If you control certain critical points - in this case, temperatures - then you will be just fine! You will find the explanations as you read the recipe, so make sure you don't miss a thing :)
To fill a 6" cake
Egg whites 99g
Butter 250g (soft and at room temperature*)
*Room temperature means that it should be easily pliable - if your room is at 19°C, then obviously it will be too cold and therefore you won't be able to work with it (like Marcelle, my Gran, used to say: "it goes without saying, but it's best saying it!". Amen to that)
The idea of the Swiss Meringue is to melt the sugar crystals in the egg whites. So pour your whites and your sugar into your mixing bowl, and seat it on a Bain-marie. Keep stirring it gently as not to cook the egg whites until you reach 50-55° C. Sugar should be completely dissolved by then.
Place your bowl on your mixer and start whisking it at almost full speed - with the whisk attachment of your mixer- until temperature goes back down. Now, what does "down" means here?? A bit of explanation.
Here is the important thing you need to know about butter: its melting point is between 28 and 35°C depending on the type of butter. So, should you start adding your butter to your 28°C + meringue, it will melt, and the result will be: soup! On the other hand, if you wait too long and your temperature drops radically (between 20-22°C), then your butter will stiffen and your whole batch will "split" - in other words, liquid and fat will separate resulting in a nice curdled texture... #funtimesahead
One of the ways to avoid that is to have a thermometer of course, and checking before you start adding your butter. Obviously this is something you will do the first few times, and when you get used to making it, you will trust the back of your (clean!) little finger to determine whereas your meringue is ready or not "receive" the butter.
So when you meringue has just reached 28-29°C, lower the speed of your mixer to medium-low and start adding your butter little by little - I personally use a little spatula and add the equivalent of a good tablespoon at a time. It is really important at this stage for your butter to be really soft and pliable (see little * in the ingredients list at the beginning)! Wait for each "spoonful" to be incorporated before adding more. When you have added almost all of your butter, suddenly your buttercream will thicken, and that's normal- it has incorporated a lot of air and has got to a temperature that is cool enough for it to get a nice thick and spreadable consistency. Just keep adding on low speed until all your butter is in. And voilà, your meringue is ready! Well, almost... As it should have quite a few air bubbles, you will have to work it with a spatula to loosen it a little and smooth it down. Voilà, NOW it's ready!
Regarding our temperatures, two things can go wrong in this process (as we all know, things don't always go as planned...):
First, your meringue was too warm, and your buttercream is very liquid. Solution: Just place your bowl in the fridge for 5-10 minutes (obviously more or less, it's up to you to judge how much it needs) and when the sides have set a bit, put it back to whisk and it should be fine!
Second common issue, when you start adding your butter, your meringue seems to be splitting and curdles. As mentioned above, that is because either your butter was added to a cold meringue, or the butter was too cold, or the room is too cold. You get my point though: it's too cold! The solution: if you have a blow torch (that works ONLY if your bowl is stainless steel), gently heat the outside of your bowl by moving the flame of your torch around the bowl as your mixer whisks the meringue. This will melt the cream around the side of you bowl and by bringing it in while whisking, it will warm up the rest of the mixture. If you do not have a blow torch, you can seat your bowl on the Bain-marie again until the ouster buttercream is a bit melted and then put it back to whisk, or just extract a small amount that you will put in a container to heat in the microwave until almost melted, and add that to the rest of your buttercream and whisk is until perfect consistency.
Another way of avoiding splitting is by keeping the whisk all the way through.
Reheating your Buttercream
A few people complain about how hard it is to re-heat a cold SMBC. It tends to split (again!) when you want to bring it back to working temperature. And again, your best bet is it leave it to come back at room temperature, then reheat a small amount of your cream in the microwave (about 10% of your total batch) and whisk it with the rest of your BC on the bowl of your standing mixer with your whisk attachment (as a rule of thumb, the whisk always works better than the paddle attachment to "rebuild"the structure of a split cream, also works with frangipane and other creams of the sort). The result: your cream will be like brand new!
This recipe works PERFECTLY with Golden Caster Sugar. It will bring a warm and delicious taste to your buttercream, almost caramel-y, perfect for a vanilla (and pistachio!!!) buttercream or for any wintery cake flavour! Just add the same quantity of Golden Sugar that you would have of the caster and let me know what you think - make sure that all the sugar crystals are well melted before putting it to whisk, even if it means heating a bit higher than 55°C!!
I do hope you love that recipe and found this post helpful in any way (although I'm sure many of you already have their own SMBC recipe!). Remember to give it a like if you loved it and keep your eyes peeled for the next post ;)