Bake the pie shells at 350 degrees for 5 minutes. Let stand until cool. Increase the oven temperature to 375 degrees.
Sauté the onion in the vegetable oil in a skillet until crisp. Add the flour. Cook for 3 minutes, stirring constantly. Add the crabmeat and shrimp. Sauté until the shrimp turn pink but not until cooked through. Add the sherry gradually, stirring constantly. Cook for 5 minutes. Spread in the partially baked pie shells
Beat the eggs in a mixer bowl. Add the cream, salt and white pepper and mix well. Pour into the prepared pie shells. Sprinkle with Swiss cheese, Parmesan cheese and parsley. Place on baking sheets. Bake for 35 minutes or until set. Let stand for 1 hour.
Note: Can store in an airtight container in the refrigerator for up to 2 days.