This is one of my go-to favorite recipes. If you haven't had Swiss Buttercream you must try this recipe. It's creamy and not super sweet so it works well for a lot of desserts. It's also really easy to fix so never worry about messing up. Follow these directions and any mistake will be avoided or fixed.
215g Egg Whites (about 7 average large eggs)**
430g Granulated Sugar
560g Unsalted Butter, unsalted and room temp
2tsp Vanilla Extract
1tsp Salt (feel free to play with more or less salt based on your taste)
1. In the bowl of a stand mixer, whisk the egg whites with the sugar just until sugar is hydrated.
2. Place the bowl over a pot of simmering water. Switch to a rubber spatula and cook until 165°F. Don't worry about mixing constantly. The sugar will help prevent the egg whites from curdling. I try to give it a small stir every few minutes but feel free to do other things while cooking.
3. Once at temp, move to the mixer and whip until airy and cooled. It can still be slightly warm especially if the butter isn't quite at room temp.
4. Add the butter a chunk at a time (about 2-4 tablespoon sized) until all is added. Whip until light and fluffy.
***If the mixture looks soupy, cool in fridge for 10-15 minute then whip. Place back in fridge as needed to cool butter and firm up.
***If the mixture is lumpy and butter is noticeable, heat the bottom of the bowl with a torch (10-15 seconds at a time) or place the bowl back on the pot of water again to heat slightly (20-30 seconds) then whip until fully mixed.
5. Add the vanilla and salt. Mix to incorporate.
This recipe makes enough buttercream to ice a 2 layer 8-inch cake. It is also my base buttercream for any flavors I do. It takes flavor easily and can be messed with quite a lot to get a lot of different results.
**Be sure to absolutely avoid egg yolks when separating the whites out. The fat in the yolk will inhibit the whites from foaming.