Frosted Chocolate Cake - Master recipes

Ingredients

• 4 large eggs, separated -
• 1/2 cup baking cocoa -
• 1/2 cup boiling water -
• 1/2 cup butter, softened -
• 1 cup packed brown sugar -
• 1 cup sugar, divided -
• 1 teaspoon vanilla extract -
• 2-1/2 cups all-purpose flour -
• 1 teaspoon baking soda -
• 1 teaspoon cream of tartar -
• 1/4 teaspoon salt -
• 1 cup buttermilk -
• Frosting: -
• 3/4 cup butter, melted -
• 3/4 teaspoon vanilla extract -
• 6 cups confectioners' sugar -
• 3 tablespoons whole milk -
• Dark or additional regular baking cocoa, optional -