Meanwhile, make a roux out of butter and flour. Gradually add the milk and keep stirring vigorously so that nothing burns. Pull the pot off the hob. Mix the mustard and the sauce and season with salt and pepper. Peel and halve the eggs and serve in the sauce.
Of course, you can also add spicy mustard to the sauce here. If you like, you can add fried onions.
Rice or potatoes and cooked vegetables (e.g. carrots, broccoli, etc.) are served with the dish. A slice of brown bread is also very tasty!