Prepare a delicious and comforting dish of beef and spinach stuffed shells using your food processor. Start by cooking jumbo pasta shells according to package instructions. In the meantime, pulse onions, garlic, and spinach in the food processor until finely chopped. Brown ground beef in a skillet and then add the chopped vegetables. Cook until the beef is fully cooked and the vegetables are tender. In a separate bowl, combine the cooked beef mixture with ricotta cheese, Parmesan cheese, and an egg. Stuff the cooked pasta shells with the beef and cheese mixture and place them in a baking dish. Top with marinara sauce and mozzarella cheese. Bake in the oven until the cheese is melted and bubbly.
