# How to Prepare:
01 - Combine peas, basil, garlic, Parmesan, pine nuts, olive oil, lemon zest, lemon juice, salt, and pepper in a food processor. Pulse until mostly smooth but still textured. Taste and adjust seasoning as needed.
02 - Spread a thin layer of butter on one side of each bread slice. Place two slices buttered side down on a clean surface. Spread 2 tablespoons of pesto on each. Top evenly with mozzarella and arugula if using. Cover with remaining bread slices, buttered side up.
03 - Heat a skillet or griddle over medium heat. Place sandwiches in the pan and cook for 3-4 minutes per side, pressing gently, until bread is golden brown and cheese is melted.
04 - Slice each sandwich in half diagonally and serve warm while cheese is still melted.