Chocolate Spoonful Cake

INGREDIENTS

• 1 cup semisweet chocolate chips and 1/2 cup semiseet chocolate shavings, shaved with a vegetable peeler from a bar of chocolate, for coating side of cake
• 1/2 teaspoon salt
• 1/2 cup unsweetened cocoa powder (not Dutch-process)
• 1/2 cup firmly packed light brown sugar
• 1 1/2 cups granulated sugar
• 2 cups sour cream
• 1 teaspoon vanilla extract
• 1 1/2 sticks (3/4 cup) unsalted butter, softened
• 1 cup confectioners' sugar
• 2 tablespoons unsalted butter
• 1 1/2 teaspoons vanilla extract
• 2 cups all-purpose flour
• 1 3/4 cups sour cream
• 1 cup heavy cream
• 3 large eggs
• 3 ounces semisweet chocolate, chopped
• 1 teaspoon baking soda