Preheat your oven to 350 degrees F.
Heat a large skillet over medium-high heat and add the olive oil. Add the ground beef and cook until no longer pink. Add the chopped onions and cook for another 3 minutes, breaking the meat into crumbles. Season with salt and pepper.
According to the package instructions, cook the pasta in a large pot of salted water. Drain and set aside. Combine the cooked pasta, ricotta cheese, egg, parsley, and 1 cup mozzarella cheese in a bowl.
Transfer the mixture to a greased baking dish and top with the cooked beef. Top with the pasta sauce.