Dark Cocoa Buttermilk Cake with Cocoa Mascarpone Frosting
Making Sour Milk:
If you don't have buttermilk on hand when preparing baked goods, substitute sour milk in the same amount. For each cup of sour milk needed, place 1 tablespoon lemon juice or vinegar in a glass measuring cup. Add enough milk to make 1 cup total liquid; stir. Let mixture stand for 5 minutes before using.