Heat 2 cm (1 in) of salted water to boiling. Add cubed potatoes, sliced apples and sugar. Once it returns to a boil, reduce heat, cover and cook for 10-15 minutes.
While the potatoes and apples are cooking away, fry the bacon. Add and fry the onion. (Drain off a bit of the grease if you have the privilege of using real bacon. If you’re using French “lardons”, you may even need to add a bit of oil for the onion.)
Place drained apples and potatoes into your serving bowl.
Top with small pieces of butter, sprinkle on nutmeg. Serve onions and bacon on top.