Ingredients:
Butter
Flour
Water
Milk
Vinegar
Pinch Salt
Pepper
Sugar
Mustard
Eggs
Preparation:
First I melt a large piece of butter, then I add flour and stir vigorously (being careful that nothing burns), then I deglaze the whole thing with milk and water (50% milk, 50% water).
Continue stirring with a whisk the whole time, otherwise lumps will form or it will burn. I let this boil gently while stirring. Then I add vinegar and sugar until it tastes good. Then comes the most important thing of all, half a pot of medium-hot mustard. Continue stirring well.
Now season with salt and pepper and let it simmer. I add the peeled eggs to the sauce so that they absorb a little of the flavor.
I really like making it with potatoes but my kids love mashed potatoes.