• Heat oven to 350°F. Line baking sheets with parchment paper.

For the cookies:

• In a large mixing bowl, cream together butter and sugars until light and fluffy. Add vanilla and eggs, one at a time, beating to incorporate after each addition.
  1 cup unsalted butter, 1 cup sugar, ¾ cup brown sugar, 1 tsp vanilla, 2 eggs
• In a separate bowl, whisk together flour, cocoa, , baking powder, baking soda and salt; gradually add the dry ingredients into the creamed mixture, beating just to combine, do not over mix.
  1 ¾ cup flour, 1 ¼ cup cocoa, 1 tsp baking powder, 1 tsp baking soda, ½ tsp salt
• Scoop the dough into about 1” balls and place about 2” apart on the prepared baking sheets. Using the bottom of a glass, slightly flatten each ball.
• Bake 8-10 minutes until puffy and just set. Cool on pans for 5 minutes before moving to racks.

For the filling:

• In a large mixing bowl, cream butter, brown sugar and powdered sugar. Add flour, vanilla and salt; mix until well incorporated and the mixture is a smooth, spreadable consistency.
  16 tbsp unsalted butter, 1 cup brown sugar, 1/2 cup powdered sugar, 1 cups flour, 1 tsp salt, 1 tsp vanilla
• Fold in the mini chocolate chips and crushed Oreos just until evenly distributed. Spread, scoop or pipe the filling onto the flat bottoms of cooled cookies and top each with another cooled cookie, pressing down gently to form a sandwich.
  2/3 cup mini chocolate chips, ½ cup crushed Oreos