Begin by boiling water in a large pot. Add salt and cook the jumbo shells according to package instructions until they're al dente. Drain and set aside.

In a skillet over medium heat, cook the ground beef until browned. Add the minced garlic and cook for another minute. Drain excess fat, if needed. Stir in the ricotta, half of the mozzarella, the egg, Italian seasoning, salt, and pepper. Mix until well combined.

Preheat your oven to 375°F (190°C). Take a spoonful of the beef and ricotta mixture and stuff each shell generously.

In a baking dish, spread a bit of marinara sauce on the bottom. Place the filled shells on top and cover with the remaining marinara sauce. Sprinkle with the remaining mozzarella and parmesan cheese.

Cover the baking dish with foil and bake in the preheated oven for 20 minutes. Remove the foil and bake for an additional 10-15 minutes until the cheese is bubbly and golden.

Garnish with fresh parsley and serve hot with additional marinara sauce on the side.