Preheat the oven to 350°F.
Add jumbo pasta shells to the boiling water. Cook until al dente according to package directions. Then, drain the jumbo pasta shells and rinse under cold water. Set aside.
In a large skillet, heat the olive oil. Add chopped onion, salt, and pepper. Saute for 4-5 minutes. Then, add minced garlic. Cook for 1-2 minutes until fragrant. Add ground beef, break it up into chunks. Cook until browned. Then, add Italian seasoning and 1 cup of spaghetti sauce. Stir until combined. Then, remove the skillet from the heat.
In a bowl, mix together ricotta, mozzarella, parmesan, and beaten egg. Then, add this cheesy mixture to the beef mixture. Mix until combined.
Grease a 9x13 inch baking pan with cooking spray. Then, add the remaining 1 cup of spaghetti sauce. Spread evenly.
Fill each jumbo pasta shell with a cheesy beefy mixture. Place them on the prepared baking pan. Top with extra parmesan and mozzarella cheeses. Bake in the preheated oven for 25-30 minutes. Enjoy!