Preheat the oven to 350℉. Line two baking sheets with parchment paper or silicone baking mats. Set aside.
In a large mixing bowl, combine the brownie mix, eggs, vegetable oil, and flour with a wooden spoon or rubber spatula. Mix until well combined.
1 box 17.8 oz. Brownie mix, I used Betty Crocker Delights Supreme Triple Chunk, 2 large Eggs, ⅓ cup Vegetable Oil, ½ cup Flour
Gently mix in the milk chocolate and white chocolate chips until incorporated.
1 cup White Chocolate Chips, ½ cup Milk Chocolate Chips
Using a cookie scoop, portion the dough onto the cookie sheets, about 2 inches apart. I use a #40 cookie scoop.
Bake for 10 to 12 minutes, until they look firm around the edges and are done in the middle. Don't overbake. They will look underdone in the middle.
Remove from the oven and allow to cool on the baking sheet for about 5 minutes before transferring the cookies to a cooling rack to cool completely. Store in an airtight container.