How do you make the green beans served at Din Tai Fung?
I think the problem lies in that the beans are not water blanched, but rather oil blanched.  The technique is called "dry frying", and is a traditional Sichuan cooking method.  The oil temp is kept low to dry out the inside while cooking the outside of the food.  After the dry frying you can then stir fry the food.  This technique should give you the required look and texture to the food.  Hope this helps.