Preheat oven to 400°. Prepare a 9 x 13 baking dish with cooking spray. Arrange Canadian bacon overlapping around perimeter of baking dish. Cover bottom with toast helping to prop up the Canadian bacon on the sides. Sprinkle with dry mustard.
Beat the egg whites until stiff. Add salt to the whites before mounding them in the baking dish. Make 8-10 depressions, spacing evenly. Bake uncovered for 2 minutes or until slightly set. Place a egg yolk in each depression. Sprinkle with salt and pepper. Bake uncovered 12-15 minutes or until whites are slightly golden and yolks are set. Serve at once.