Cook pasta shells
Cook Italian sausage. Wipe out pan when finished and use same pan for spinach.
Sautee garlic for a few seconds in a pan. Add fresh spinach. I add in large batches, allowing spinach to cook down before adding more. Keep all spinach in pan until it has all been cooked. Remove spinach to a colander and allow spinach to cool. Once cool, squeeze out all liquid. This takes a lot of squeezing. Keep rotating spinach in your hands and squeeze until all liquid is removed.
Coarsely chop spinach
Combine ricotta, parmesan, egg and seasonings together in a bowl.
Add chopped spinach and fold until combined
Add cooled sausage, be careful to not add any of the grease.
Carefully stuff each pasta shell with 3 tablespoons of cheese filling. Place each stuffed shell in a greased baking dish with a layer of marinara sauce. Continue filling all shells until dish is full.
Drop spoonfuls of sauce around the filled shells. Place diced mozzarella on top of shells. Sprinkle remaining parmesan cheese over top
Cover dish with foil and bake at 375 for 30 minutes. Remove foil and continue cooking for an additional 20 minutes. Turn broiler on for an additional 5 minutes and cook until the cheese is slightly browned.
Remove from oven and allow dish to rest for 10 minutes Garnish with fresh herbs and serve with additional marinara sauce