You know, I'd eaten this a couple of times and made it myself (throwing in handfuls of peppery watercress as I did so) a few more before I realised it was, give or take, the River Cafe's recipe - by which I mean to say that although the amounts and full list of ingredients vary, it is an English seaside version of their fabulous original. I suppose that's how you know something's become a classic: it just seeps its way into the culinary language.
Crab is, I think, hugely underrated - so much better than lobster, and much cheaper. You can use frozen crab meat for this, but it's best to get a fishmonger to cook and pick out the meat for you.
Don't let the fact that a pestle and mortar is indicated put you off: this is fabulously easy to make.
Recipe posted by Nigella