Start by mixing ricotta, one cup of mozzarella, Italian seasoning, and the egg in a bowl. You will know it is ready when it is creamy and well-blended, smelling aromatic and inviting. This filling will make your shells deliciously rich. Just be careful not to overmix, or it can become too dense.
Take each cooked jumbo shell and fill it with the ricotta mixture using a spoon or piping bag. As you stuff them, feel the shells' smooth edges and see them plump up with cheesy goodness. Each one should be generous, but avoid overstuffing, so they do not burst during baking.
Spray your baking dish with cooking spray to prevent sticking. You will want a nice even sheen to really keep those shells intact. The dish will feel slippery under your fingers. Skipping this step can lead to a messy cleanup, so do not forget it!
Pour about a cup of marinara sauce on the bottom of the dish and spread it out. You will catch the scent of tomatoes and herbs wafting as you do this. This step keeps the shells moist while baking, so keep an eye on how much you add—too little might dry them out.
Place the stuffed shells in the sauce-lined dish, opening side up. You can visualize a tidy row of shells ready to shine. Just make sure they are not crowded together, or they will not cook evenly. It is tempting to pack them in, but they need space to breathe!
Spread the remaining marinara sauce over the stuffed shells evenly. You will see it glisten as it envelopes each shell, creating a saucy layer. This helps prevent the tops from drying out while baking. Do not skip on this sauce; it really ties it all together!
Cover the shells with the remaining mozzarella and sprinkle grated parmesan on top. Watch as they glisten as you sprinkle, promising a cheesy, bubbly finish. This creates that irresistible crust, but do not pile it too high; you want it to melt nicely and not burn.
Once it is out of the oven, sprinkle chopped parsley over the top for a pop of color. You will love the fresh aroma that fills your kitchen, inviting everyone to the table. Just let it sit for a few minutes before serving to avoid burning anyone’s tongue.