Coffee-Chocolate Layer Cake with Mocha-Mascarpone Frosting

INGREDIENTS

• Bittersweet chocolate curls (optional)
• 2 8-ounce containers chilled mascarpone cheese*
• 1 cup buttermilk
• 1 1/2 teaspoons baking soda
• 2 cups cake flour
• 2 cups (packed) golden brown sugar
• 1/3 cup natural unsweetened cocoa powder
• 3 large eggs
• 3/4 cup (1 1/2 sticks) unsalted butter, room temperature
• 1 1/2 cups chilled heavy whipping cream, divided
• 1 1/3 cups sugar
• 3/4 teaspoon salt
• 1 tablespoon instant espresso powder
• 4 teaspoons instant espresso powder dissolved in 3/4 cup hot water
• 3/4 cup natural unsweetened cocoa powder
• 11/2 teaspoons vanilla extract