The best kind of sandwiches are definitely cookie sandwiches -- with the exception of the muffuletta and sub sandwich which are equally awesome. The cookie sandwich is a simple concept. You take two cookies, whichever kind you like, and fill them with frosting (cream cheese, buttercream, etc.) or chocolate ganache. If you want to take it one step further, you can even top the cookie sandwich with more frosting, sprinkles or powdered sugar.
Essentially, a cookie sandwich means that you get to eat two cookies (plus frosting!) and it looks like you're just having one. And if you have two cookie sandwiches, it means you've actually scored four cookies. It's pure genius!