Wash, clean and thinly slice the beans. Bring salted water with savory to the boil, add the beans and cook for about 10 minutes. Drain and collect the cooking water.
Melt the butter in a saucepan and sauté the diced bacon and onion until translucent. Add the flour and sweat. Measure out 1/4 L of the stock and pour in while stirring. Stir in the milk and simmer the sauce over low heat for 10 minutes. Add the beans and heat. Season with nutmeg, salt and pepper and serve sprinkled with parsley.