For the sauce, heat the oil in a casserole dish. Add the shallots, leek, carrot, fennel, garlic and celery and fry for 10 minutes over a low heat until soft.
Add the tomato purée, chopped tomatoes, white wine and brandy and cook to reduce by half.
Add the chopped salmon and cod and cook for five minutes.
Add the stock, bay leaf, tarragon and cayenne pepper, then cover and simmer for 40 minutes.
Blend the mixture, then pass through a sieve (push the mix through the sieve to get as much flavour as possible).
For the stew, pour the sieved sauce back into the casserole dish and bring up to the boil. Add the fish and vegetables and simmer for 3-4 minutes or until the fish is cooked through.
When cooked, stir in the double cream and mix through the parsley.
Stir in the lemon juice and season with salt and freshly ground black pepper. Serve with crusty bread and garlic mayonnaise.
