1. Preheat the oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving an overhang on two sides for easy removal. Lightly grease the parchment.
2. Prepare the brownie batter according to the package directions. Fold in the chocolate chips and chocolate sprinkles, then spread the batter evenly into the prepared pan.
3. Bake the brownies for 10 minutes less than the time listed on the package.
4. Remove the pan from the oven and gently arrange the Spider-Man cookies over the partially baked brownies, leaving a little space between each cookie. Sprinkle the exposed brownie batter with the red, white, blue, and yellow sprinkles.
5. Return the pan to the oven and bake for 8 to 12 minutes more, or until the cookie dough is lightly golden around the edges and the brownies are just set. A toothpick inserted into the brownie portion should come out with a few moist crumbs, but no wet batter.
6. Let the brookies cool completely in the pan. Lift them out using the parchment paper.
7. Cut into a fun mix of squares, rectangles, and triangles so each piece shows off the Spider-Man cookies in a different way.

Tips

• For the cleanest slices, refrigerate the brookies for 30 to 60 minutes before cutting.
• Store in an airtight container at room temperature for up to 3 days.