01 -
In a mixing bowl, combine cooked spaghetti with marinara sauce, tossing until evenly coated and avoiding excess sauce to prevent soggy bread.
02 -
Spread softened butter evenly on one side of each bread slice.
03 -
Place two bread slices, buttered side down, on a preheated skillet over medium heat. Add half of the mozzarella cheese to each slice, then spoon the spaghetti mixture on top. Sprinkle with Parmesan and Italian seasoning if using. Layer the remaining mozzarella over the spaghetti.
04 -
Top each pile with the other bread slices, buttered side facing up.
05 -
Cook each sandwich for 3 to 4 minutes per side, pressing lightly with a spatula, until the bread is crisp and golden brown and the cheese is thoroughly melted.
06 -
Slice each melt in half and serve immediately, with extra marinara sauce for dipping if desired.