Making these cookies is as enjoyable as eating them. Let’s dive into the process:

1. Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
2. In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt.
3. In a larger bowl, cream the butter and sugar together until light and fluffy, about 3 minutes.
4. Add the egg and vanilla extract to the butter mixture, mixing until well combined.
5. Gradually incorporate the dry ingredients into the wet ingredients until just combined. Stir in the mini chocolate chips.
6. Scoop tablespoon-sized amounts of dough onto the prepared baking sheet, spacing them about 2 inches apart.
7. Bake for about 8-10 minutes, or until the edges are set. Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack.
8. For the cookie dough filling, cream together the butter and brown sugar in a bowl until smooth. Add the milk and vanilla extract, mixing until combined.
9. Gradually mix in the flour until the dough is smooth, then stir in the mini chocolate chips.
10. Once the cookies are completely cooled, spread a generous amount of cookie dough onto the bottom of one cookie and sandwich with another.

Enjoy the process and make it a family affair. The kids will love helping out, and the result is worth every bit of the chocolatey fun.