Preheat your oven to 375°F (190°C). Lightly grease a 9 × 13-inch baking dish. Bring a large pot of salted water to a boil and cook the jumbo shells according to the package instructions, stopping 1–2 minutes before they are fully tender. Drain carefully and arrange them on a tray to prevent sticking.

1. Cook the shrimp.Heat the olive oil in a skillet over medium heat. Add the chopped shrimp and cook for 2–3 minutes, stirring occasionally, until pink and opaque. Let them cool slightly before mixing with the other filling ingredients.
2. Prepare the seafood filling.In a large bowl, combine the cooked shrimp, crab meat, ricotta, half of the mozzarella, Parmesan, egg, minced garlic, parsley, Italian seasoning, paprika, salt, and black pepper. Mix gently until everything is evenly combined.
3. Make the creamy sauce.Melt the butter in a saucepan over medium heat. Add the garlic and cook for about 30 seconds until fragrant. Whisk in the flour and cook for 1 minute, stirring constantly.
4. Add the milk and cream.Slowly pour in the milk while whisking to prevent lumps. Stir in the heavy cream, Italian seasoning, paprika, salt, and black pepper. Simmer for 3–5 minutes until the sauce thickens slightly.
5. Finish the sauce.Remove the saucepan from the heat and stir in the Parmesan cheese until melted and smooth. If the sauce becomes too thick, add a small splash of milk to loosen it.
6. Fill the pasta shells.Spoon a thin layer of creamy sauce into the bottom of the prepared baking dish. Carefully fill each cooked shell with the seafood mixture and arrange them in a single layer over the sauce.
7. Add the remaining sauce and cheese.Pour the rest of the creamy sauce evenly over the stuffed shells. Sprinkle the remaining mozzarella and Parmesan over the top for a golden, cheesy finish.
8. Bake until bubbly.Cover the dish loosely with foil and bake for 20 minutes. Remove the foil and bake for another 8–10 minutes, until the cheese is melted and lightly golden and the sauce is bubbling around the edges.
9. Rest and serve.Let the shells rest for 5 minutes before serving. Garnish with fresh parsley and serve warm with garlic bread, a crisp green salad, or roasted vegetables.