Slice and dice the vegetables and mince the garlic.
Heat a wok or frying pan over medium heat and add the oil. Saute the onions, celery, carrots and garlic until the onions are translucent - about 5 minutes. Add the basil, salt and pepper and juice from the lemon. Add the mushrooms and cook for 1-2 minutes. Then add the beans and cook until everything is warm.
Spoon 1/4 of the bean mixture into each of the lettuce leaves and serve.
Use 2 cans of beans, rinsed and drained, or make them from scratch. (See How to use a Pressure Cooker). Any type of bean will work.
You can also add walnuts, pine nuts, almonds or bell pepper.