Preheat the oven to 350 F. Cook the giant pasta shells according to package directions until al dente. Drain and reserve. Separate them to make sure they don’t stick together once they cool down.
Season the marinara sauce: place the marinara sauce un a medium-sized saucepan and season with one teaspoon Italian seasoning, ½ teaspoon garlic powder, and a pinch of cinnamon. Simmer for 10 minutes and reserve.
Make the cheese filling: in a medium-sized bowl, mix the ricotta, 1 ½ Italian 4 cheese blend, egg, minced onion, chopped parsley, salt and pepper.
Spoon about 1 ½ cups of Marinara sauce into the bottom of a 9x13-inch baking dish and make sure it covers the bottom evenly
Fill each cooked shell with about a tablespoon of cheese filling and place them on top of the sauce.
Spoon the remaining sauce over the shells
Sprinkle the remaining ½ cup Italian 4 cheese blend on top of the shells and sauce. Bake until the cheese is melted and everything is heated through, about 30-35 minutes. Serve with freshly chopped basil on top.