Preheat oven to 350*F and spray a 9x9 inch baking pan with cooking spray
Cream butter on medium high speed with an electric mixer. Add sugar and vanilla; mix until fluffy.
Add eggs, mixing well after each.
Next, add flour, baking soda, and salt. Mix until all ingredients are combined.
Divide dough in half. Press half of dough into the prepared pan. Arrange Oreos over cookie dough, then top with remaining cookie dough. (The easiest way to do this is to just lay flat pieces of dough over the top and sort of press the seams together.)
Bake for 25-30 minutes, or until cookie dough is golden brown on top. Remove from oven and cool completely. Cut into squares and enjoy!
Recommended: drizzle with melted chocolate and cover with sprinkles!