Peel and wash the potatoes and cut them into halves or quarters depending on their size. Cover and cook in salted water for about 20 minutes. Prick the eggs and boil them hard for about 10 minutes.
In the meantime melt butter in a pot. Dust with flour and sauté until golden brown. Add 1/2 l water and cream bit by bit while stirring. Stir in broth and mustard, bring to the boil and simmer for 4-5 minutes.
Season with salt, pepper, 1 pinch of sugar and vinegar.
Wash parsley, shake dry and chop finely. Quench eggs cold, peel them and keep them warm in the mustard sauce. Drain potatoes and sprinkle with parsley. Arrange everything.