1. Prepare cake mix according to package directions for a 9x13 cake.
2. Once cake comes out of the oven, allow it to cool for just a couple of minutes.
3. Then, with a wooden spoon handle or some other similarly-sized object, begin poking holes in the warm cake. You want the holes to be fairly big so that the pudding has plenty of room to get down in there. Be sure to poke right down to the bottom of the cake.
4. In a medium bowl, whisk together dry pudding mix with 4 cups of milk. Whisk until all the lumps are gone.
5. Pour pudding over cake. Taking care to get right into the holes as much as possible. Spread it all out and using the back of the spoon, gently push pudding down into the holes.
6. Put the cake into the fridge to set and cool (about 2 hours). If you have anything hanging out in your fridge that is stinky, be sure to cover your cake.
7. Once your cake has completely cooled, spread on whipped topping. Spread it out evenly over the pudding layer.
8. If you haven't done so already, crush your cookies. Leave some of the pieces big. It's nice to have a bit of a crunch when you eat the cake.
9. Spread crushed cookies onto the top of the cake. You can do this part immediately before serving the cake if you like. This will ensure the cookie bits are crunchy when you serve it.
This cake needs to be kept refrigerated.
