Boil the pasta shell in water until al dente. Do not overcook or they will fall apart when yo try to stuff them. Drain and set aside to cool
For the filling:
Drain the crab meat on paper towels until any excess moisture is removed. To a medium bowl add the ricotta cheese, Parmesan cheese, and Mozzarella cheese. Stir with a spoon until combined. Gently fold in the crab meat. Set aside.
For the sauce:
Melt the butter over medium heat. Add the flour and cook for one minute stirring constantly. Slowly add the milk, whisking constantly until smooth. Cook for 2-3 minus. Remove from stove. Add the cheese, white pepper and salt. Stir until the cheese is completely melted. Pour the cheese sauce into the bottom of a casserole dish or into individual, oven proof baking dishes. Spoon the filling into the pasta shells, dividing it equally. You'll have to estimate how much to put in each shell. Place the filled shells on top of the white sauce and bake in a 350 degree oven until hot, bubbly and heated through. Pop under the broiler for more color and a little crust. Sprinkle with chopped parsley, extra cheese and drizzle with pesto sauce.
Approximate nutrition information is provided as a convenience and courtesy only. You are encouraged to do your own calculations if precise data is required.