Dice the bacon and leave it in a large saucepan. Add the flour and roast until brown. Deglaze with the milk and bring to the boil, stirring constantly. Add the mustard and stir well. Season to taste with pepper and salt. Beat the eggs one after the other in a ladle and carefully and slowly add them to the sauce, they should not run apart
For 5 - 10 minutes, depending on how soft or firm you like the eggs, let set over low heat and then season the sauce with vinegar to taste.