A crispy, buttery sourdough grilled cheese loaded with pizza sauce, mozzarella, pepperoni, mushrooms, peppers, onion and olives. Ready in under 20 minutes.
Heat a panini press to medium, or heat a large skillet or grill pan over medium-low heat.
Spread the softened butter evenly over one side of each bread slice. Place 2 slices butter-side down on a cutting board and spread each with 2 tablespoons of pizza sauce.
Top each sauced slice with 1 ½ slices of mozzarella. Divide the pepperoni, mushrooms, bell pepper, red onion, black olives and diced tomatoes between the two sandwiches, sprinkle with Italian seasoning if using, and finish with the remaining mozzarella.
Spread the remaining pizza sauce on the unbuttered side of the last 2 bread slices and set them on top, sauce-side down and butter-side up.
In a panini press, cook for 4 to 6 minutes, until the bread is golden and the cheese is melted. In a skillet, cook for 3 to 4 minutes per side, pressing gently with a spatula; cover the pan while the first side cooks to help the cheese melt.
Let the sandwiches rest for 1 minute, then slice in half and serve with warm pizza sauce for dipping.
Notes
For softer vegetables, sauté the mushrooms, pepper and onion in 1 teaspoon of oil for 2 to 3 minutes before building the sandwiches. Drain the diced tomatoes well so the bread doesn't get soggy.