Here's what you need:
Cookie Dough (chocolate chip is best, but peanut butter or others work too)
Ice Cream (preferably vanilla).
Flatten the cookie dough into the bottom of a pan (don't make it too thin, or it will burn...maybe about 1/2 -3/4 inch thick). You can use a cake pan, a cookie sheet, a casserole dish, whatever. And you can make the "cookie" as big or as small as you want it.
Put in the oven (at 350 degrees) for 6 minutes or so. Every oven is different, so you'll want to watch the first time you make this. You are going to bake your giant cookie until it is between 1/2 and all the way done. you don't want to bake it completely, you want it to still be a little gooey.
As soon as you pull it out of the oven, scoop the ice cream on top and immediately eat!