Cook the Pasta Shells:

1. Boil the jumbo pasta shells according to the package instructions until al dente. Drain and set aside.

Make the Alfredo Sauce:

1. In a saucepan, melt the butter over medium heat. Add the minced garlic and sauté for 1 minute. Slowly whisk in the heavy cream and bring it to a gentle simmer. Stir in the Parmesan cheese until melted and smooth. Season with nutmeg, salt, and pepper.

Prepare the Filling:

1. In a large bowl, combine the shredded chicken, chopped broccoli, ricotta cheese, 1/2 cup mozzarella cheese, Parmesan cheese, egg, garlic powder, salt, and pepper. Mix well.

Assemble the Shells:

1. Preheat the oven to 375°F (190°C). Spread a thin layer of Alfredo sauce on the bottom of a greased baking dish. Stuff each pasta shell with the chicken and broccoli mixture and arrange them in the dish.

Add the Sauce and Bake:

1. Pour the remaining Alfredo sauce over the stuffed shells and sprinkle the top with the remaining mozzarella cheese. Cover with foil and bake for 20 minutes. Remove the foil and bake for an additional 10 minutes or until bubbly and golden.

Serve:

1. Let the dish rest for 5 minutes before serving. Garnish with parsley or additional Parmesan if desired.