Cook the shells. Bring a large pot of salted water to a boil. Add the jumbo shells and cook until just shy of al dente, about 1 minute less than package directions. Drain, rinse under cool water, and drizzle with a little olive oil to prevent sticking.

Mix the filling. In a bowl, combine ricotta, 1 1/2 cups mozzarella, 1/2 cup Parmesan, egg, half the minced garlic, parsley, lemon zest, 1/2 teaspoon salt, and a few grinds of pepper. Stir until creamy and well mixed.

Make the Alfredo sauce. In a skillet or saucepan, melt butter over medium heat. Add the remaining garlic and cook 30 seconds until fragrant. Pour in heavy cream and broth; bring to a gentle simmer. Stir in the remaining 1/2 cup Parmesan, a pinch of nutmeg, 1/2 teaspoon salt, and pepper to taste. Simmer 2–3 minutes until slightly thickened. Remove from heat. The sauce will thicken more in the oven.

Prep the baking dish. Spoon about 1 cup of the Alfredo sauce into a 9x13-inch baking dish, spreading to coat the bottom. This keeps the shells from sticking and drying out.

Stuff the shells. Fill each shell with about 2 tablespoons of the ricotta mixture. Nestle them into the sauced baking dish, open side up, creating snug rows.

Top and cover. Pour the remaining Alfredo sauce evenly over the shells. Sprinkle with the remaining 1/2 cup mozzarella and a little extra Parmesan if you like a bubbly, golden top.

Bake. Cover the dish loosely with foil and bake at 375°F (190°C) for 20 minutes. Remove foil and bake another 10–15 minutes until the sauce is bubbling and the cheese is lightly golden around the edges.

Finish and serve. Let the shells rest 5–10 minutes so the sauce settles. Garnish with chopped parsley and a twist of black pepper. Serve warm with a crisp salad or steamed veggies.