Step 1: Cook the Pasta Shells

1. Bring a large pot of salted water to a boil.
2. Add the jumbo pasta shells and cook 1-2 minutes less than package instructions (since they will continue cooking in the oven).
3. Drain and rinse with cold water to stop the cooking process. Set aside.

Step 2: Prepare the Seafood Filling

1. In a large bowl, combine the ricotta cheese, cream cheese, mozzarella, and Parmesan. Mix until smooth.
2. Stir in the lemon zest, parsley, garlic powder, onion powder, salt, and black pepper.
3. Add the chopped shrimp and crab meat, gently folding everything together. Set aside.

Step 3: Make the Garlic Parmesan Sauce

1. In a medium saucepan, melt butter over medium heat.
2. Add the minced garlic and sauté for 30 seconds to 1 minute until fragrant.
3. Stir in the flour and cook for 1 minute, stirring constantly.
4. Gradually pour in the heavy cream and broth, whisking to prevent lumps.
5. Add the Parmesan cheese, Italian seasoning, and red pepper flakes. Stir until the sauce thickens, about 3-4 minutes.
6. Season with salt and pepper to taste, then remove from heat.

Step 4: Assemble the Stuffed Shells

1. Preheat the oven to 375°F (190°C).
2. Spread ½ cup of the Parmesan sauce on the bottom of a greased baking dish.
3. Fill each cooked pasta shell with the seafood mixture and arrange them in the dish.
4. Pour the remaining creamy sauce evenly over the shells.

Step 5: Bake and Serve

1. Cover the baking dish with foil and bake for 20 minutes.
2. Remove the foil and bake for an additional 5-10 minutes until bubbly and golden.
3. Garnish with fresh parsley and extra Parmesan, then serve hot with a squeeze of lemon juice.