Ingredients
- 8 ounces high-quality milk chocolate (such as Lindt, Perugina, or Valrhona), chopped
- 1/4 cup (1/2 stick) unsalted butter, room temperature
- 2/3 cup sour cream
- 4 teaspoons light corn syrup
Preparation
Step 1
Place chocolate in large metal bowl. Set bowl over saucepan of simmering water and stir until melted and smooth. Remove bowl from over water. Add butter and stir until melted, then add sour cream and corn syrup and whisk until smooth.
Let frosting stand at room temperature until thick enough to spread, about 20 minutes.
Using serrated knife, trim top of cakes to make level. Cut each cake horizontally in half. Place 1 cake layer, cut side up, on platter.
Spread 1/4 cup frosting over, leaving 1/2-inch border. Top with second cake layer, cut side down. Spread 1/4 cup frosting over, leaving 1/2-inch border. Top with third cake layer, cut side up. Spread 1/4 cup frosting over, leaving 1/2-inch border. Top with remaining cake layer, cut side down. Spread 1/3 cup frosting over top and sides.
Chill until frosting is set, about 30 minutes. Keep remaining frosting at room temperature.
Spread remaining frosting evenly over top and sides of cake.
DO AHEAD Can be made 2 days ahead. Cover with cake dome and store at room temperature.