Sauté mushrooms and green pepper in 2 tablespoons butter in a large skillet until tender. Remove vegetables, and set aside. Add flour and salt to pan drippings, stirring until smooth. Cook 1 minute, stirring constantly. Gradually add half-and-half; cook over medium heat, stirring constantly, until thickened and bubbly. Stir in chicken. Reduce heat to low.
Add sherry, lemon juice, and onion juice, mixing well; cook 3 minutes or until bubbly. Combine egg yolks, softened butter, and paprika in a small mixing bowl; beat well. Add yolk mixture to chicken mixture, stirring constantly. Cook 2 to 3 minutes. Stir in pimiento and reserved vegetables.
Spoon chicken mixture into a chafing dish. Spoon evenly into patty shells to serve.