Ingredient:

• 3/4 cup butter, softened
• 1-1/2 cups sugar
• 1 large egg
• 1 teaspoon vanilla extract
• 1 cup buttermilk
• 3/4 cup sour cream
• 2 cups all-purpose flour
• 2/3 cup baking cocoa
• 1 teaspoon baking soda
• 1/4 teaspoon salt
• ERMINE FROSTING:
• 1/2 cup all-purpose flour
• 2-1/2 cups whole milk
• 1-3/4 cups confectioners' sugar
• 1/2 teaspoon salt
• 1-3/4 cups butter, softened
• 1-1/2 teaspoons vanilla extract
• 16 ounces semisweet chocolate, chopped
• 1/2 cup butter, cubed
• 1-1/2 cups heavy whipping cream