Approx. 4 servings
Half a stick of butter
2-3 Tbsp flour
Milk (and/or water from potatoes)
Melt the butter in a small pot and add the flour stirring constantly. When the flour and butter has been mixed well together, add milk/potato water stirring constantly until the right consistency is reached. Add salt, pepper (optional). Take the sauce off the heat and add chopped parsley just before serving.