Bring 4 cups of water to a boil in a medium-size saucepan. Wash the string beans and cut iff the stem ends. When the water has reached a rolling boil, plunge in the string beans annd allow to cook for 5-7 minutes, until they are firm but crisp. Heat the butter in a medium size-skillet. When it is foamy add the garlic and sesame seeds and cook, stirring constantly, until the garlic is slightly browned. Add the string beans and continue to cook, stirring constantly, until the string beans are coated with thte gerlic and sesasme seeds. Serve hot.