In a large bowl, combine the salmon, onion, bread crumbs and butter. Stir in the egg yolks, lemon juice, parsley, salt and pepper.
In a small bowl, beat the egg whites on high speed until stiff peaks form. Fold into salmon mixture.
Transfer to a greased 8-in. x 4-in. loaf pan. Place in a larger baking pan. Add 1 in. of hot water to larger pan. Bake at 350° for 40-45 minutes or until a knife inserted near the center comes out clean. Let stand for 10 minutes before slicing.
Meanwhile, in a small saucepan, melt the butter. Stir in flour until smooth; gradually add milk. Bring to a boil; cook and stir for 1-2 minutes or until thickened. Stir in olives. Serve with salmon loaf. Yield: 4 servings.