In a small saucepan sauté onions in butter
Stir in flour salt and pepper until blended gradually whisk in milk and cream. Bring to a boil
Cook and stir for two minutes or until thickened.
Remove from the heat stir in the rice shrimp crab meat water chestnuts lemon juice pimentos parsley and 1/2 cup cheese.
Transfer to a greased 2-1/2-qt. baking dish.
Bake at 350 for 25-35 minutes or until heated through.
Sprinkle with remaining cheese