Peel and finely chop the onion. Slice and then dice the aubergine into about ½ in / 1 cm cubes. ‘Fry’ the onion and aubergine in a large non-stick pan until soft and wilted and beginning to brown a little. Add the tomatoes and stock, and continue cooking until the flavour has begun to develop. Husk the corn cobs, and cut the kernels from the cobs by standing each one vertically on a chopping board and slicing down with a sharp knife, cutting off as much of the flesh as possible. Add the corn kernels to the soup, together with salt and pepper to taste. Bring to the boil, and simmer for a few minutes, until the corn is just tender. Stir in the chopped parsley and serve.
The flavour of the soup can be heightened with a dash of lemon juice, balsamic vinegar or fino sherry. Extra body can be added to the soup by putting a handful or so of rice in the pot when you have first brought the stock to the boil.