Preheat your indoor pizza oven with the temperature set to temperature specified on your brownie mix, typically 350℉. When fully heated, set the heat balance dial (if equipped) to Bottom 5/Top 5.
Grease a Detroit-Style pizza pan with unsalted butter. You want to make sure the butter covers the entire interior surface and corners.
Prepare the brownie mix as instructed on the box. Fold in 1/2-cup to 1-cup peanut butter chips.
Spread the brownie batter out evenly in the prepared Detroit-Style pizza pan. Make sure the batter fully reaches the corners.
Use a spoon, add dollops of peanut butter in two straight lines lengthwise down the the top of the brownie batter. Using a carving fork or spoon spread the peanut butter out into tight lines to create the signature sauce "racing stripes" Detroit-Style pizza is known for. (Note: A carving fork is useful as helps some of the peanut butter better mix with the batter below.)
Bake according the directions on the brownie mix. Using a Detroit-Style Pizza Pan typically requires using the full baking time for brownie mixes as the batter is often thicker.
Let cool fully in the pan. Run a metal spatula between the edge of the baked brownies and the pan to make sure they are not stuck to the sides. Transfer the brownies to a cutting board to slice into squares. Serve immediately.