From 1911:
Chop the whites of four hard boiled eggs and mix with one cup of white sauce, seasoning as desired; pour over strips of rounds of toast; then rub the yolks of the eggs over the whole, through a strainer. Serve on toast platter and garnish with parsley. This is enough for six pieces of toast. An excellent breakfast dish.
For hard boiled eggs, let the water come to a boiling point; then turn the fire down so it will stop boiling and put in the eggs; let them stand for from 40 to 45 minutes in water below the boiling point. The whites of eggs cooked in; boiling water are apt to be tough.