Heat a frying pan until hot and then add the one tablespoon of olive oil.
Season the fish with salt and freshly ground black pepper and place the fillets skin-side down into the frying pan. Fry for one minute.
Remove from the frying pan and place on a baking tray.
Place the fillets in the oven to cook for four minutes, then remove and allow to rest.
To make the sauce, de-shell all the shrimps and put them to one side. Reserve the shells.
Heat the one tablespoon of oil in a deep non-stick frying pan until hot. Add the shallot and leek and cook gently for one minute until lightly browned.
Add the garlic and sauté for a further minute.
Add the tomato purée and shrimp shells and cook for four minutes.
Add the brandy to the pan and scrape up any browned bits. Add the fish stock and simmer for a further four minutes.
Add the cream and season with salt and freshly ground black pepper to taste.
Allow the mixture to cool slightly, then place the mixture into a food processor and blend until smooth.
Place a fine sieve over a clean saucepan and pour the mixture through the sieve into the saucepan.
Place the saucepan onto a medium heat and bring the sauce to simmer. Add the shelled shrimps.
For the potatoes, boil the potatoes in salted water until they are tender when pierced with a knife. Drain well and set aside.
Place the potatoes in a bowl and crush them with the back of a fork. Season with salt and black pepper to taste.
Add the crab, tomato, spring onion, half of the lemon juice, olive oil and dill and mix together.
To serve, pile the potatoes in the centre of the plate. Place the fish on top with the skin-side up. Squeeze the remaining lemon juice over the top and brush with olive oil. Spoon the sauce around the fish.