3 egg whites (120 g)
¾ cup granulated sugar
A pinch of cream of tartar
A pinch of salt
2 sticks (1 cup) butter at room temperature
1 tablespoon vanilla
Bring a pan of water to a simmer. Choose a bowl that fits over the pan without touching the water. Combine the egg whites, the granulated sugar, cream of tartar, and salt in the bowl and heat while whisking over the simmering water until the mixture thickens and reaches 150° F.
Once the egg whites and sugar reach 150° F pour into the bowl of an electric mixer fitted with a whisk attachment and beat until shiny and the bottom of the bowl is cool to touch.
Pinch off pieces of butter about 1 tablespoon at a time and toss into the meringue. Beat until the pieces disappear then toss in a few more repeating until all the butter is incorporated.
Once all the butter is incorporated add the vanilla and stir until combined.
For chocolate buttercream stir in 7 ounces of melted chocolate (70% cocoa) with the vanilla.
Pipe the frosting onto cupcakes or into macarons. Frosts 12 regular sized cupcakes or fills one batch of macarons.