1. Finely chop the garlic and shallots, slice the pepper, cut the cherry tomatoes into two and dice the courgette and aubergine. Heat the olive oil in a large pan and add the vegetables, chopped tomatoes, water, salt and pepper, and leave to simmer for around 20 minutes.
2. Heat up the poaching water for the cod and add the salt, then poach the cod fillets for around 8 minutes until they start to flake.
3. Serve the ratatouille with the olives and basil, topped with the poached cod.