Chocolate Blackout Cake

Name: Chocolate Blackout Cake
Ingredients: 1 cup whole milk; 1/3 cup sugar; 2 tablespoons cornstarch; 1 teaspoon vanilla extract; 1 large egg; 2 ounces semisweet chocolate, finely chopped; 12 ounces semisweet chocolate, finely chopped; Pinch of salt; 1 1/2 cups plus 2 tablespoons heavy cream; Basic Chocolate Cake, recipe follows, baked and cooled; Cooking spray; 1 cup unsweetened cocoa powder (natural or Dutch process); 2 1/2 cups all-purpose flour; 2 cups sugar; 1 1/2 teaspoons baking powder; 1 teaspoon baking soda; 1 teaspoon salt; 3 large eggs, at room temperature; 3/4 cup vegetable oil; 1/2 cup sour cream; 2 teaspoons vanilla extract