Wash the beans and trim the ends. Cook the beans in salted water with the savory for 10 minutes. Then drain and chill (if the beans are not processed immediately, you can put them in a sieve with ice cubes so that they keep their green color)
Heat the butter in a saucepan, then sauté the onion with the garlic until translucent. Pan the beans in the butter and heat briefly. If you like, you can sprinkle parsley over the beans.