Fish and Shrimp Sandwich in a Lemon Yogurt Sauce

Name: Fish and Shrimp Sandwich in a Lemon Yogurt Sauce
Ingredients: 1 tablespoon yeast; 2 cups warmed milk; 1/4 cup butter, melted; 1/4 cups sugar; 4 cups all-purpose flour; 1/2 tablespoon salt; 4 tablespoons butter, for cooking fish and shrimp; 1/2 cup chopped cucumber; 1/2 cup grated carrots; 1/2 cup chopped celery; 1/4 cup chopped black olives; 4 tablespoons fresh lemon juice; 1 tablespoon lemon pepper; 1 tablespoon dill weed; 1 tablespoon dried parsley; 1/2 teaspoon salt; 2 pounds cod fish; 2 pounds large shrimp; 1 cup grated sharp Cheddar; 1 cup lemon yogurt; 4 slices bread