Start by boiling the jumbo shells until just slightly firm to the bite. I always remove them a couple of minutes early since they will bake later. Rinse with cold water to stop cooking and prevent sticking.
In a skillet, melt butter and whisk in flour to form a smooth base. Slowly add cream, milk, and wine while stirring continuously. Then mix in garlic, Parmesan, seasoning, and let it cook until silky and thick.
In the same skillet, sauté shrimp and lobster in butter for a few minutes until fully cooked. Be careful not to overcook, as seafood becomes rubbery quickly. Set aside once tender and juicy.
In a large bowl, combine cream cheese, cooked seafood, crab, spinach, mozzarella, Parmesan, and seasoning. Mix everything until well blended and creamy. The filling should be rich but easy to scoop.
Spread the prepared sauce at the bottom of your baking dish. Stuff each shell with the seafood mixture and arrange them neatly. Sprinkle remaining mozzarella on top for that golden finish.
Cover the dish with foil and bake until heated through and bubbly. Remove foil toward the end to let the cheese turn lightly golden. Let it rest briefly before serving for the best texture.