Blue swimmer crab soup

Serves 4-6

I spent a few days over the New Year down at Mitch Tonk's house in Brixham, Devon. We cooked up a storm on New Year's Eve with lightly salted pollack cooked in olive oil with the most buttery mash ever (pommes mousseline actually) and delicious Dexter beef chops cooked on the Okabashi grill – the rest of my stay turned into a bit of a blur.

During the day, the younger kids went crabbing off the marina pontoon with Robin Hancock of Wright Bros, the oyster bar in Borough Market. They proudly brought back a few blue swimmer crabs in their bucket and that gave me the idea of making a sauce to go with a whole baked turbot that we were planning to eat that night. The kids perched themselves on stools near the cooker armed with a wooden spoon and I took them through the process of making crab sauce. It was delicious; so much so that most of it was consumed before dinner, and we had to settle for Hollandaise instead. I'm sure the kids didn't expect their crabbing expedition to turn into a cook-up with such delicious results. So why don't we use blue swimmer crabs more? Even the poor old spider crab doesn't get much of a look-in. In Spain and France they are on display in most fishmongers for soups and stews, but here they are just regarded as a pest to fishermen because they eat all the bait before the brown crabs can get to it.

500-600g blue swimmer crabs
1tbsp vegetable oil
1 small onion, peeled and roughly chopped
1 small leek, trimmed and roughly chopped
3 garlic cloves, peeled and roughly chopped
1/2 tsp fennel seeds
10-15 strands of saffron
A few sprigs of thyme
1 bay leaf
40g butter
2tbsp tomato purée
3tbsp flour
1 glass of white wine
1.5litres fish stock, or a couple of good fish stock cubes in 1.5litres of hot water
100ml double cream
Salt and freshly ground white pepper

Put the crabs in the freezer for about 30-40 minutes then remove them and chop them into pieces. Heat the vegetable oil in a large heavy-based saucepan and fry the crabs over a high heat for about 5 minutes, stirring every so often until they begin to colour. Add the onion, leek, garlic, fennel seeds, saffron, thyme and bay leaf, and continue cooking for another 5 minutes or so, until the vegetables begin to colour. Add the butter and stir well, then add the tomato purée and flour, stir again and cook for a minute or so over a low heat. Add the white wine, then slowly add the fish stock, stirring to get rid of any lumps. Bring to the boil, season with salt and pepper, and simmer gently for 1 hour.

Blend the soup in a liquidiser or a strong food processor then strain through a fine-meshed sieve.

Return to a clean pan, season with a little salt and pepper, if necessary, and bring to the boil. To serve, add the cream and adjust the seasoning again, if necessary, and stir well.