Six-Layer Chocolate Cake with Toasted Marshmallow Filling & Malted Chocolate Frosting

INGREDIENTS

• :
• 2½ cups + 1 tablespoon all-purpose flour
• 3 cups granulated sugar
• 1 cup + 1 tablespoon Dutch-process cocoa powder
• 1 tablespoon baking soda
• 1½ teaspoons baking powder
• 1½ teaspoons salt
• 3 eggs, at room temperature
• 1½ cups buttermilk, at room temperature
• 1½ cups strong black coffee, hot
• ¾ cup vegetable oil
• 4½ teaspoons vanilla extract
• 16 large marshmallows
• 1 cup powdered sugar
• 1 cup unsalted butter, at room temperature
• ½ teaspoon vanilla extract
• 1 (7½-ounce) jar Marshmallow Fluff
• 2 cups unsalted butter, at room temperature
• 4 cups powdered sugar
• ¾ cup Ovaltine Classic
• 1 tablespoon vanilla extract
• Pinch of salt
• 8 ounces semisweet or dark chocolate chocolate, melted and cooled
• ½ cup heavy cream