Preheat oven to 400 degrees. Spray a 2 quart baking dish with nonstick cooking spray. Set aside.

In a large pot, cook gnocchi according to package directions adding spinach leaves for the last minute of cooking. Drain and then return to pot.

In a large saucepan, cook pancetta over medium heat until browned and the fat has rendered, about 8-10 minutes. Remove from pan with slotted spoon to a paper towel-lined plate.

To the fat left in the pan, add butter and mushrooms and cook until softened, about 5-7 minutes. Add garlic and continue to cook for 1 minute. Stir in flour to combine and cook for 1 minute. Slowly whisk in milk and cook until mixture thickens and begins to bubble. Season with salt, pepper and nutmeg. Stir in all but 2 tablespoons of parmesan cheese. Pour over gnocchi and spinach mixture. Add pancetta and fresh mozzarella. Stir gently until well combined. Transfer to prepared baking dish. Sprinkle with remaining parmesan cheese.

Bake for 25 minutes until golden and bubbly.