Begin by boiling a large pot of salted water. Once it reaches a rolling boil, add the jumbo pasta shells. Cook them for about 8-10 minutes, or until they are al dente. Drain the shells and rinse them under cold water to stop the cooking process.
In a large mixing bowl, combine ricotta cheese, cooked shrimp, crab meat, shredded mozzarella cheese, minced garlic, and lemon juice. Season with salt, pepper, and fresh herbs. Mix everything until well combined.
Take each cooled pasta shell and fill it generously with the seafood mixture. Place the stuffed shells in a greased baking dish.
In a saucepan, melt butter over medium heat. Add flour and whisk for about a minute. Gradually pour in milk, stirring constantly until the sauce thickens. Add shredded mozzarella cheese and stir until melted. Season with salt and pepper to taste.
Pour the creamy sauce evenly over the stuffed shells. Sprinkle breadcrumbs on top for added crunch.
Preheat your oven to 375°F (190°C). Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the top is bubbly and golden brown.
Once baked, let the seafood stuffed shells cool for a few minutes. Garnish with fresh herbs and a squeeze of lemon juice. Serve warm and enjoy!