Preheat your oven to the temperature specified on the brownie mix box.

Prepare the brownie batter according to the instructions on the box.

Grease a 12-inch pizza pan or line it with parchment paper.

Pour the brownie batter onto the prepared pizza pan and spread it evenly to create a thin layer.

Bake the brownie base in the preheated oven for the time stated on the box, or until a toothpick inserted into the center comes out clean.

Let the brownie base cool completely on the pan before proceeding.

Spread the chocolate frosting evenly over the cooled brownie base to resemble pizza sauce.

Sprinkle the mini marshmallows, chocolate chips, chopped strawberries, and crushed nuts (if using) evenly over the frosting as toppings.

Slice the brownie pizza into wedges and serve immediately.