Have you tried one of those mock Oreo recipes before? You know the ones with the "1 cake mix" in the ingredient list. I don't know about you, but those don't taste like oreos to me. Oreos aren't just any old chocolate sandwich cookie. They have to be thin and crispy and with an intense chocolate taste.
Several years ago I found the perfect cookie make Oreo type sandwich cookies with. It's a recipe from Martha Stewart that I adjusted to fit what I was looking for.
Chocolate Sandwich Cookies:
1/2 c butter
1/2 c sugar
1 large egg
1 cup cocoa powder (yes. 1 full cup)
1/2 c + 2 T flour
Cream the butter and sugar. Add in the egg. Mix in the cocoa powder and flour. Divide the dough in half and wrap each in plastic wrap. Refrigerate the dough for one hour.
Preheat oven to 350 degrees. Using powdered sugar on the counter to prevent sticking, roll out dough to 1/8" thickness. Cut with 2" cookie cutter and place 1/2" apart on cookie sheets. Bake until you smell the chocolate, aprox. 12 minutes.
I do suggest you use parchment paper on your cookie sheets because these have a tendency to stick quite badly.
I used a basic American butter cream to frost the centers. I have four rules for better butter cream:
1. you should use at least twice as much butter as you do cream. Meaning if you use 1/4 cup butter you should only use 2 T of heavy cream.
2. Use lots of vanilla. I like to use 2 t as a starting point. I may add more later.
3. Use salted butter or at least add a pinch of salt to your frosting. You won't believe what a difference it makes.
4. Beat the holy heck out of it. I beat my butter cream for at least five minutes and as long as ten minutes. This makes it fluffy and light and it makes sure the powdered sugar has time to dissolve so you don't get that raw taste.
You could also use a nice ganache (Martha used ganache with mint extract), or jam, or cream cheese frosting in your cookies.