Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan and prepare the boxed cake mix according to the instructions. Pour batter into the pan and bake for 25–30 minutes until a toothpick comes out clean.

After cooling, poke holes evenly across the surface of the cake with a skewer or fork, about 1 inch apart, all the way to the bottom.

In a mixing bowl, whisk the vanilla pudding mix with the required amount of milk until well combined. Let stand for 2–5 minutes to thicken if using instant pudding.

Pour the pudding over the cake, spreading it gently to fill the holes evenly.

Cover with plastic wrap and chill for at least 2 hours to allow the pudding to set.

Once chilled, spread the chocolate frosting evenly over the top, slice into squares, and serve chilled.