01 - Lay out all bread slices. Spread a thin, even layer of softened butter on one side of each slice.
02 - Flip two slices buttered side down. Spread 1 tablespoon of marinara sauce evenly across each slice.
03 - Distribute half the shredded mozzarella cheese evenly over the sauced bread slices.
04 - Arrange pepperoni slices in a single layer over the mozzarella. Omit this step for vegetarian version.
05 - Sprinkle the remaining mozzarella and half the Parmesan cheese over the pepperoni layer.
06 - Top each sandwich with the remaining bread slices, buttered side facing outward.
07 - Heat a non-stick skillet over medium heat. Place sandwiches in pan and cook for 3–4 minutes per side, pressing gently with spatula, until bread turns golden brown and cheese melts completely.
08 - During the final minute of cooking, sprinkle dried oregano, garlic powder, and remaining Parmesan cheese over the tops of sandwiches.
09 - Transfer sandwiches to cutting board, slice diagonally in half, and serve immediately with warm marinara sauce for dipping.