Preheat oven to 325 degrees and spray a pan with cooking spray (oven temp and cook time will depend on pan size and material. Go by the directions on your brownie mix box)

Prepare brownie mix according to package directions.

Spread ½ the brownie batter into prepared pan.

Place Pop Tarts on top of batter. I laid mine out whole and then trimmed some with kitchen shears to fill in around the one edge

Spread the remaining batter on top of the Pop Tarts

Cook according to package directions based on pan size and type. Under cook them by just a few minutes to keep them from drying out.

Once the brownies are done, top with mini marshmallows

Broil for just a couple minutes and pull them out when they are toasted and brown on top.

Allow the brownies to cool slightly, then slice into squares.