Preheat Oven:

• Preheat oven to 375°F (190°C).

• Lightly grease a 9×13-inch baking dish.

Cook the Pasta Shells:

• Boil jumbo shells in salted water until al dente according to package directions.

• Drain and rinse with cold water to stop cooking. Set aside.

Prepare the Beef Filling:

• In a skillet, heat olive oil over medium heat.

• Add chopped onion and cook for 2–3 minutes.

• Add ground beef and cook until browned.

• Stir in garlic, Italian seasoning, salt, and pepper.

• Drain excess grease and let mixture cool slightly.

Mix the Cheese Filling:

• In a large bowl, combine ricotta cheese, egg, 1 cup mozzarella, Parmesan cheese, and the cooled beef mixture. Mix well.

Stuff the Shells:

• Spread a layer of marinara sauce (about 1 cup) on the bottom of the baking dish.

• Fill each cooked shell with the beef and cheese mixture and place in the dish, open side up.

Add Sauce and Cheese:

• Spoon remaining marinara sauce over the stuffed shells.

• Sprinkle with the remaining 1/2 cup mozzarella cheese.

Bake:

• Cover with foil and bake for 25 minutes.

• Remove foil and bake an additional 10–15 minutes, or until bubbly and cheese is melted.

Serve:

• Garnish with chopped fresh basil or parsley if desired.

• Serve hot with garlic bread or a green salad.