Prepare the Brownies: Bake the brownie mix according to package directions and let the brownies cool completely in the pan. Once cooled, cut into approximately 2-inch squares and set aside. For best results, use dense or slightly fudgy brownies so they hold together when wrapping.
Make the Cookie Dough: In a large bowl, beat the softened butter, brown sugar, and granulated sugar together until light and creamy. Add the milk and vanilla extract and mix until well combined. Slowly add the flour and mix until a soft dough forms. Fold in the mini chocolate chips. The dough should be thick but pliable enough to roll. Chill briefly if it feels too soft to handle.
Shape the Dough Balls: Scoop about 1 tablespoon of cookie dough and roll into small balls. Place them on a lined tray or plate. You should get around 20–24 balls, depending on size. Chill them for 15–20 minutes to help them firm up.
Wrap with Brownies: Take one brownie square and gently flatten it in your palm. Place a chilled cookie dough ball in the center and wrap the brownie around it, pressing gently to seal the dough inside. Roll between your hands to smooth out the shape. Repeat with remaining pieces.
