First make the couscous: peel and dice the onion. Deseed the sweet peppers and dice. Deseed the chilli and chop finely. Remove the stalks from the parsley and chop the leaves coarsely, reserving a few whole leaves for garnish. Shred the mint leaves.
Boil the amount of water specified on the couscous packet and pour it over the couscous. Stir for 2—3 minutes to stop lumps forming. Juice the lemon and stir in, together with the prepared vegetables and herbs. Stir in the olive oil and season. Chill.
Make the soup: heat the vinegar and dissolve the sugar in it, then allow to cool.
Meanwhile, blanch the tomatoes briefly in boiling water, then refresh in cold water. Peel, deseed and dice them.
Mix the passata and fresh tomato. Shred the basil and stir it in. Season. Now drip in the vinegar mix, a teaspoonful at a time, tasting after each addition until you like the balance. Chill.