Preheat oven to 350.
Using a stand or hand mixer, cream the softened butter and sugar together. Add eggs one at a time and mix until they're completely blended into the butter and sugar.
Mix in cocoa, flour, and salt.
Once the batter is completely blended together, fold in the chocolate chips & mint chips (reserve some mint chips for the very top) and stir.
In a square 8x8" or 9x9" lightly greased glass baking dish, pour in HALF of the brownie batter and spread evenly on the bottom.
Line the 16 cookies evenly across the batter.
Add the remaining brownie batter on top of the cookies and spread evenly with a spatula. Sprinkle some mint chips across the top.
Bake in oven for 20-25 minutes.
Remove from oven and serve hot with a scoop of vanilla ice cream, or allow to cool and then chill in the fridge and serve cold. These are good either way!