1. Preheat the oven to 350°F and lightly grease a 9×13-inch baking dish. Prepare the cake batter using orange juice or orange soda instead of water, then bake for 25–30 minutes until a toothpick inserted in the center comes out clean.

2. Allow the cake to cool for 5 minutes, then use the handle of a wooden spoon to poke holes about 1 inch apart across the entire surface, reaching almost to the bottom.

3. Whisk the orange gelatin into the boiling water until completely dissolved, then stir in the cold water. Slowly pour the mixture evenly over the cake so it fills the holes.

4. Cover the cake and refrigerate for 2–3 hours, allowing the gelatin to fully set inside the cake.

5. Whisk the vanilla pudding mix with the cold milk for about 2 minutes until slightly thickened. Gently fold in the whipped cream to create a light vanilla mousse.

6. Spread the mousse evenly over the chilled cake and refrigerate for another 30 minutes before serving.

7. Decorate with fresh orange zest or mandarin orange segments if desired. For neat slices, dip your knife in hot water and wipe it dry before each cut.