Put a pan of water on to boil and blanch the celery for 3-4 minutes to soften. Drain and set aside.
If you have a deep fryer, set it up for the aubergines and peppers. Deep fry in batches until browned and sticky-looking, then set aside. Alternatively, cook them in batches of olive oil.
In a sauté pan fry the onion until starting to brown. Add the cap