Cook sausage in large skillet over medium-high heat until well browned, about 10 minutes (stir sausage as it cooks to break into pieces).

Add mushrooms and Italian seasoning; cook and stir until mushrooms are tender, sausage is no longer pink in center and liquid has evaporated 3 to 5 minutes. Remove from heat.Press all excess liquid from spinach.

Stir spinach, ricotta cheese, 1/4 cup Parmesan and pepper into sausage mixture: mix well.

Divide sausage mixture evenly between 4 bread slices; top with remaining 4 slices to form sandwiches. Gently press down on sandwiches with palm of hand.

Beat eggs and milk in shallow dish or pie plate.

Melt 1 tablespoon butter on griddle over medium-low heat.

Briefly dip both sides of each sandwich in egg mixture, letting excess drip off.

Fry sandwiches on hot griddle, turning once, until golden brown, about 10 minutes. Add more butter to griddle as needed.

Sprinkle top of each sandwich with 1 tablespoon of remaining Parmesan.

Serve with warm spaghetti sauce.