Spread the butter mixture evenly over one side of the bread slices. Lay the bread butter side up on a sheet tray.
Over medium-low heat, place a piece of bread butter side down in a skillet. Top with a slice of mozzarella, 6 pepperoni slices, another slice of mozzarella, 6 more pepperonis, and a final slice of mozzarella.
Place another piece of bread on top, butter side up. Cook until the bottom is golden brown (about 3-5 minutes), then flip and cook until the other side is golden and cheese is melted
Serve immediately with warm pizza sauce for dipping.
