Sausage Stuffed Shells

Preheat oven to 350°F. 
Bring a large pot of salted water to a boil. Cook pasta shells 1 minute before al dente, strain, and rinse with cool water to prevent overcooking.
Meanwhile, in a cast-iron skillet, cook sausage until fully cooked through and browned. About 5-7 minutes. Use the tip of a spatula to break the sausage into the smallest chunks possible as it cooks. Season with salt and pepper to taste and remove the pan from the heat.
Transfer the sausage to a medium bowl with ricotta, basil, garlic, parmesan cheese, and egg. Stir until fully incorporated and creamy. Place 1 cup of marinara in the bottom of the now-empty skillet.
Cut a 1-inch hole in a pastry bag or corner of a large Ziploc bag. Transfer the ricotta filling to the bag and fill each shell to the top with ricotta. You can alternatively fill shells with a spoon.
Arrange shells in the skillet as tightly as possible. You can usually fit 20-22 shells in a 12-inch cast iron skillet. Top each shell with a heaping tablespoon of marinara. Layer the entire dish with about 1 cup of shredded mozzarella (more is OK too).
Bake for 20-25 minutes or until cheese is fully melted and golden. Finish with a quick broil to give the cheese a little sear if desired. Let cool for 5 minutes, top with extra chopped basil, and serve immediately.