1teaspoon imported mustard, such as Dijon or Düsseldorf
Preheat the oven to 400 degrees.
Rinse the trout and pat dry inside and out. Set aside.
Heat 2tablespoons butter in a saucepan and add the celery, onion, and green pepper. Cook until the onion is wilted. Add the crabmeat and bread crumbs. Add the egg, parsley, and salt and pepper to taste. Mix well.
Sprinkle the trout inside and out with salt and pepper to taste. Stuff the trout with the crabmeat mixture. Arrange the trout in a buttered baking dish. Dot each trout with 3tablespoons butter. Pour the fish stock and 3tablespoons sherry around the fish. Bake, uncovered, 20 minutes, basting often.
Pour the cooking liquid into a saucepan and bring to the boil. Using the fingers, pull off and discard the skin from both sides of the fish but not from the heads and tails. Using the fingers, remove the thin backbones from the backs of the fish. Arrange the trout on a hot serving dish. Keep warm.
Add the paprika and cream to the sauce and bring to the boil. Beat the yolk, and add a little of the hot sauce to it. Return this mixture to the saucepan, stirring rapidly. Do not boil. Stir in the mustard and remaining sherry and strain the sauce over the fish.