Preheat the oven to 350°F
Line a baking sheet with parchment paper
In a bowl, combine 1 box brownie mix, 2 eggs, 1/3 cup vegetable oil, and 1/4 cup all-purpose flour
Stir until a thick dough forms
Add chocolate chips, nuts, or other mix-ins if desired
Scoop tablespoon-sized portions onto the baking sheet
Leave space between each cookie
Bake for 8 to 10 minutes
Remove when the edges are set and the centers look slightly soft
Cool on the baking sheet for 5 minutes
Transfer to a wire rack to cool completely