Chocolate Mousse Cake Recipe

Name: Chocolate Mousse Cake Recipe
Ingredients: 3/4 cup (3 3/4 ounces) all-purpose flour; 1/3 cup (3/4 ounce) cocoa powder; 3/4 teaspoon baking soda; 1/2 cup plus 2 tablespoons (about 4 1/3 ounces) packed light brown sugar; 2/3 cup sour cream; 1/3 cup vegetable oil; 1 large egg; 1 teaspoon instant espresso powder; 2 teaspoons pure vanilla extract, divided; 1/4 teaspoon salt; 1/3 cup (2 1/3 ounces) granulated sugar; 3 large egg yolks; 2 3/4 cups plus 2 tablespoons heavy cream, cold, divided; 20 ounces bittersweet chocolate, finely chopped, divided; 4 ounces semi-sweet chocolate, finely chopped (see note); Confectioners' sugar for dusting cake