Set oven to 350°F (175°C). Line a baking sheet with parchment.

Mix brownie mix, eggs, and oil in a large bowl until smooth; don’t overmix.

Combine flour, brown sugar, granulated sugar, vanilla, and 1/2 cup chocolate chips. Adjust with milk (if dry) or flour (if sticky).

Roll dough into 1-inch balls (12–16 pieces).

Flatten brownie batter, place a cookie ball in the center, and seal completely.

Place on sheet, 2 inches apart. Bake 15–18 minutes until edges set.

Cool slightly on a wire rack before serving.