Preheat your oven to 375˚F. While it heats up, cook the pasta shells in a big pot of salted water, just like the package says. Give them a few good stirs while they cook so they don’t stick together. Once they’re done, drain the water, then fill the pot with cold water to cool the shells down and keep them from clumping.

Heat 1 tablespoon of olive oil in a deep pan over medium-high heat. Toss in the chopped onion and sauté for 3 to 5 minutes until it’s soft and golden. Next, add the minced garlic along with 1/2 teaspoon of salt, 1/4 teaspoon of pepper, and 1/4 teaspoon of oregano. Stir everything nonstop for another minute until the garlic smells amazing. Pour in 3 cups of marinara sauce, bring it all to a nice even boil, then let it simmer for 2 minutes. Once it’s ready, pour the sauce into the bottom of a 9x13 casserole dish.

In a big mixing bowl, toss in the ricotta cheese, mozzarella, parmesan, egg, parsley, salt, and pepper. Mix it all together really well until everything’s creamy and fully combined—it should look like cheesy perfection!

Scoop about half an ice cream scoop of the cheese mixture into each shell—just enough to fill them without overstuffing. Line them up in a single layer over the marinara sauce in your casserole dish. Then sprinkle the remaining 1 cup of mozzarella cheese all over the top.

Cover the dish with foil and bake for 30 minutes, until the sauce is bubbling around the edges. Take off the foil and broil for 2 to 4 minutes to get that cheese nicely golden on top. Once it’s out of the oven, sprinkle with fresh parsley and serve it up warm!