Carefully separate the yolks from the whites and set aside. Chop whites to about 1-inch pieces. Set aside.
In medium sauce pan, melt butter over medium-low heat. Sprinkle flour over melted butter and stir to form a paste. Slowly stir in milk, whisking until smooth after each increment is added. Once desired thickness is reached, add Parmesan and salt and pepper. If sauce is too thick, add milk 1 tablespoon at a time. Add chopped egg whites.
Over medium bowl, press yolks through a sieve with the back of a spoon, forming a powder.
Toast several pieces of bread and spoon sauce over top. Sprinkle with powdered yolks. Serve immediately.