1

To make the custard, whisk together the sugar, cornstarch, and salt in a heavy medium saucepan. Whisk in milk and egg and set over medium heat. Cook, stirring, until the custard boils. Cook, stirring, until thickened. Remove from the heat; stir in the vanilla. Press plastic wrap directly onto the surface of the custard; refrigerate.

2

Preheat the oven to 350°F. Spray a 9-inch round baking pan with nonstick spray. Line with a wax-paper round; spray with nonstick spray.

3

To make the cake, whisk together the flour, baking powder, and salt in a medium bowl. Whisk together the milk, 1⁄2 cup of the sugar, the oil, egg, and orange zest in a large bowl; stir in the flour mixture just until blended. With an electric mixer on medium speed, beat the egg whites in a medium bowl until soft peaks form. Add the remaining 3 tablespoons of sugar, 1 tablespoon at a time, beating just until firm peaks form. With a rubber spatula, gently fold the beaten whites into the batter until no streaks of white remain. Pour the batter into the pan. Bake until a toothpick inserted into the center comes out clean, about 35 minutes. Let cool completely in the pan on a rack. Run a knife around the cake to loosen it from the pan. Invert.

4

To make the glaze, combine the glaze ingredients in a microwavable bowl. Microwave on High until the chocolate is melted, about 30 seconds. Stir until smooth; let cool.

5

Split the cake layer in half with a long serrated knife. Place the bottom layer, cut side up, on a serving plate. Spread the custard evenly over the layer, leaving a 1⁄2-inch border. Place the remaining layer on top, rounded side up. Spoon the chocolate glaze over the top, allowing it to drip down the side of the cake. Refrigerate until set. Yields 1⁄12 of cake per serving.