1. Preheat oven to 350°F (175°C). Prepare cake mix according to package instructions (or your homemade recipe). Bake in a 9×13-inch pan and allow to cool. Cut into 1-inch cubes.

2. In a medium saucepan, combine cranberries, sugar, orange juice, and zest. Cook over medium heat until cranberries burst and sauce thickens slightly. Let cool.

3. In a medium saucepan, whisk together sugar and cornstarch. Gradually whisk in milk and egg yolks. Cook over medium heat, stirring constantly, until thickened. Remove from heat and stir in butter and vanilla. Cool slightly.

4. Beat heavy cream with powdered sugar and vanilla until stiff peaks form.

5. Assemble trifle in a large glass bowl or individual cups: layer cake cubes, cranberry sauce, custard, and whipped cream. Repeat layers, finishing with whipped cream. Garnish with fresh cranberries or chocolate shavings.