Ingredients
• 2 cups all-purpose flour
• 1 1/2 cups granulated sugar
• 1/2 cup light brown sugar, packed
• 3/4 cup unsweetened cocoa powder
• 2 teaspoons baking powder
• 1 1/2 teaspoons baking soda
• 3/4 teaspoon salt
• 3/4 cup oil, canola or vegetable
• 2 eggs
• 1 teaspoon vanilla extract
• 6 tablespoons milk
• 1/3 cup sour cream
• 1 cup boiling water
For the topping:
• 10.5-ounce package mini marshmallows
• 1/2 cup butter (1 stick)
• 6 tablespoons milk
• 3 heaping tablespoons unsweetened cocoa powder
• 1 teaspoon vanilla extract
• 3 cups powdered sugar