In one saucepan make a rather thin Béchamel sauce properly seasoned with salt, pepper and nutmeg; in another one cook in butter two shallots finely chopped; when they are browned add a drop of wine vinegar, a tablespoonful of French mustard, a pinch of paprika and a pinch of curry powder; stir all this well, add it to the Béchamel sauce, with which you incorporate the yolk of one egg and a small glass of fresh cream. Cook slowly au bain marie, whipping all the time and adding one by one little pieces of butter. See that it is highly seasoned, and if necessary rectify the seasoning. Keep the sauce as hot as possible, the saucepan still standing in hot water.
Meanwhile fry your eggs either in butter, or in bacon fat according to taste, turning them once. They should be well fried outside and soft inside. Dispose them on toast previously fried. Just before serving pour the Sauce Diable all round and all over the eggs.