Makes 48 "sticks" (2 ¼ in. by 1 inch)
Preparation time: 20 minutes
Baking time: 20 to 23 minutes

1 package (18.25 ounces) plain German chocolate cake mix
2 large eggs
¼ cup vegetable oil
1 tablespoon water
2 cups confectioner's sugar, sifted
2 tablespoons half-and-half or whole milk
4 tablespoons butter (½ stick), 2 tablespoons at room temperature
½ teaspoon pure peppermint extract
2 ounces unsweetened chocolate, coarsely chopped

Place a rack in the center of the oven and preheat the oven to 350º F. Set aside an ungreased 13- by 9-inch pan.

Place the cake mix, eggs, oil and water in a large mixing bowl. Blend with electric mixer on low speed until the dough is well combined, 1 minute. Transfer the batter to the ungreased pan and smooth it evenly to the sides with a rubber spatula. Place the pan in the oven.

Bake the cake layer until it puffs up and cracks and the edges look crusty, 20 to 23 minutes. Don't overbake this layer; it should look jiggly when you shake the pan. Remove the pan from the oven and place it on a rack to cook for 10 minutes. Set aside.

For the filling, place the confectioner's sugar, half-and-half, 2 tablespoons room temperature butter, and peppermint extract in a medium-size mixing bowl. Blend with an electric mixer on low speed to incorporate, 30 seconds. Increase the mixer speed to medium and beat until fluffy, 1½ minutes. Spread this filling thinly over the warm cake, using a long metal spatula or dinner knife to reach the edges. Let the cake rest until the filling forms a thin crust on top, 10 minutes.

Meanwhile, prepare the glaze: melt the chocolate and remaining 2 tablespoons butter in a small glass bowl in the microwave oven on high power for 45 seconds and stir until the chocolate has melted. Pour this warm chocolate glaze over the cake, and spread it with the metal spatula or dinner knife until it reaches the edges.

Slice the cake and serve warm, or cover the pan with aluminum foil and chill until firm, then slice and serve.

Store these bars, covered in plastic wrap or aluminum foil, in the refrigerator for up to 1 week. Or freeze them, wrapped in foil, for up to 3 months. Thaw the bars overnight in the refrigerator before serving.