Bake your cake according to package instructions in two 8 or 9 inch round cake pans. Let cool.
Trim tops if necessary to make them even and level.
Set out your ice-cream for a few minutes for it to soften up a bit, but you don’t want it runny!
On your cake stand lay out a couple of pieces of plastic wrap criss-crossed in a cross shape. Later you will be wrapping this all around your cake to hold everything together while it freezes.
Set your first cake layer on top of the plastic wrap.
Spread half of your ice-cream in a thick layer on top of the cake.
Crumble your cookies up (You can crumble them in a ziploc type bag with a rolling pin), and then spread them over the first layer of ice-cream.
Now the next step you can do one of two ways depending which you find easier: either freeze your cake for a while, and then add another layer of ice-cream and your final cake layer, OR go ahead and add the second layer of ice-cream and then cake, and THEN wrap and freeze. Freezing in between layers seems to be a little easier way to work with it because it firms everything up, but it takes a little longer.
Then it gets frozen one last time for a few hours or until your celebration.
When you’re ready to serve your cake, remove it from the freezer, top with some extra crumbled cookies for decoration, and serve immediately. Keep any leftovers in the freezer!