Crush the crab shells or break them up as small as possible. Wash, peel and roughly chop up the vegetables. Heat the oil in a large, heavy-based saucepan, add the vegetables and sweat for at least 5 minutes, then add the shells and continue sweating for a further 4 minutes. Pour in the brandy, reduce it slightly, then stir in the tomato purée followed by the fish stock, herbs, saffron and peppercorns. Bring to the boil and simmer for at least 3 hours. Alternatively, put the stock in an ovenproof pan and simmer for 3 hours in a moderate
To clarify the consommé, wash and peel the vegetables and mince or chop very finely with the fish. Mix in the tomato purée and the egg whites followed by the cold stock; the stock must be cold at this stage or it will cook the egg white. Set the pan over a high heat and bring almost to the boil, stirring occasionally to prevent the consommé from sticking. Stop stirring the consommé when it has almost reached boiling point otherwise it will cloud. Allow to simmer for at least 1 hour, then gently strain the liquid through muslin and season to taste.