01 - Place bread slices on a cutting board. Spread 1/2 tablespoon softened butter evenly on one side of each slice.
02 - On the unbuttered side of two slices, spread 1 1/2 tablespoons basil pesto evenly across the surface.
03 - Layer mozzarella slices over the pesto-coated bread. Add provolone if using, then top with tomato slices and grated Parmesan. Season with freshly ground black pepper.
04 - Place remaining bread slices on top with buttered side facing outward to ensure golden crisping during cooking.
05 - Heat a large nonstick skillet or griddle over medium-low heat for 2-3 minutes until properly warmed.
06 - Transfer sandwiches to the preheated skillet. Cook for 3-4 minutes, pressing gently with a spatula, until bottom bread develops deep golden-brown color.
07 - Carefully flip sandwiches and cook another 3-4 minutes until bread is golden and cheese is completely melted.
08 - Remove from heat and let sandwiches rest for 1-2 minutes. Slice diagonally and serve immediately while hot.