Milk chocolate can be on the sweet side, so I added a little bittersweet to this recipe to tame it just a bit. Melt both chocolates, beat them together with butter and milk, then add some powdered sugar and a touch of vanilla. I’m not going to lie, the frosting’s still sweet, so spread it on less sweet cakes and cupcakes to balance out the flavors.
Game plan: This recipe makes enough buttercream to frost an 8-inch layer cake or 24 cupcakes.
Once made, let the buttercream sit at room temperature until you’re ready to use it, up to 3 hours. If you’re not going to use it within 3 hours, refrigerate it in a container with plastic wrap directly touching the surface for up to 3 days. To use refrigerated buttercream, let it sit at room temperature until softened, then beat it in the bowl of a stand mixer fitted with a paddle attachment until smooth and fluffy.
6 ounces milk chocolate, coarsely chopped
3 ounces bittersweet chocolate, coarsely chopped
3 sticks unsalted butter, at room temperature
2 tablespoons whole milk
1 teaspoon vanilla extract
1/4 teaspoon fine salt
2 1/2 cups powdered sugar
Fill a medium saucepan with 2 inches of water and bring it to a boil over high heat. Reduce the heat to low so the water is just simmering. Place the milk chocolate and bittersweet chocolate in a heatproof bowl large enough to sit over the water without touching it. Place the bowl over the saucepan and stir until the chocolate has melted and is smooth. Set aside until cooled slightly but still pourable, about 5 to 10 minutes.
Beat the butter in the bowl of a stand mixer fitted with a paddle attachment on medium-high speed until light and fluffy, about 3 minutes.
Add the milk and beat until incorporated. Pour in the melted chocolate and mix until completely incorporated. Add the vanilla and salt and mix until incorporated. Stop the mixer and scrape down the sides of the bowl and the paddle with a rubber spatula.
Turn the mixer to low and slowly add the powdered sugar until it’s incorporated and the mixture is creamy. Increase the speed to high and mix until lightened in color and fluffy, about 1 minute.