Clean the beans and break them into bite-sized pieces. Cook in a little salted water with the savory sprigs for 10 to 15 minutes until al dente, then rinse in cold water and drain.
Clean the spring onions, cut in half and cut into fine strips. Wash and quarter the cherry tomatoes.
Gradually mix the mustard with the white wine vinegar. Season with salt and freshly ground pepper, then beat in the olive oil.
Finally, fold the beans in a tall salad bowl with the chopped savory under the vinaigrette and let them steep until consumed.
Sprinkle the lettuce with chopped parsley before serving.