Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine melted butter and sugar until smooth.
Add eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
Sift together flour, cocoa powder, and baking powder, then fold into the wet mixture until just combined.
Stir in the semi-sweet chocolate chips until evenly distributed.
Prepare a baking dish by greasing it or lining it with parchment paper.
Pour the brownie batter into the prepared dish and spread it evenly.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
While baking, prepare the cookie dough by creaming together the softened butter, brown sugar, and granulated sugar.
Add milk and vanilla to the mixture, and beat until well combined.
Gradually mix in flour and mini chocolate chips until just incorporated.
Once the brownies have cooled, scoop out small balls of cookie dough.
Using a cookie scoop, place a dollop of cookie dough on top of each brownie square.
Allow the cookie dough to set on the brownie base for a few minutes before serving.
