Bring a large pot of water to a boil. Add your jumbo shells and boil for 5 minutes. Remove and place on an oiled baking tray to cool.
Bring a large saucepan to medium-high heat. Season ground beef with 1 teaspoon salt and ½ teaspoon of black pepper. Brown ground beef until you can no longer see any pink. Remove the ground beef with a slotted spoon and clean out the pan.
Return the pan to medium heat. Add 2 tablespoon olive oil. Stir in 1 clove minced garlic. Saute for 1 minute and then stir in the crushed tomatoes. Add 1 teaspoon salt and basil leaves. Bring the sauce to a simmer and then add the ground beef back in. Simmer for 15 minutes.
Preheat oven to 375℉. In a large bowl, combine ricotta, egg, parmesan, ½ cup mozzarella, 1 teaspoon salt, ½ teaspoon black pepper, parsley, and the rest of the minced garlic. Mix well.
Using a spoon fill each shell with the ricotta filling. Spoon a layer of sauce into the pyrex dish. Place your stuffed shells into the pan. I like to place mine with the opening on the bottom and press each shell tightly up against one another until they are all stuffed into the dish. Top with the rest of the sauce and then add a layer of mozzarella. Bake in the oven for 20-25 minutes or until the cheese and sauce are bubbling. Serve hot!
Notes
Don't cook the shells completely through but also be aware that they are cooking evenly by stirring them often in the pot.
Make sure the shells are packed tightly up against each other, otherwise they will ooze out their filling.
If you don't use all the sauce, save some for leftovers!