Watercress Sauce

Watercress is at its best in spring, when the chalk streams of Hampshire and Dorset are running cold and the leaves come up dark, glossy, and properly peppery. That's the moment for this sauce. Not the bagged stuff in November that tastes of nothing and bruises in the fridge. The real thing, in season, with a bite to it.

This is a sauce for a dinner party where you want to do something a little better than ordinary without making a fuss. A piece of grilled sea trout, a seared steak, a fillet of plaice barely coloured in butter. Pour the sauce around it from a small jug at the table. The colour alone does most of the work. A vivid, almost shocking green, the kind of green that makes people lean forward.

The method is barely a method. You soften a shallot, reduce some wine, add cream, wilt the watercress, blend. The whole thing takes less time than it takes to grill the fish you're serving it with. The trick, if there is one, is to wilt the watercress fast and blend it faster. Heat is the enemy of that colour. Get it in the jug while it's still singing.

A recipe is a conversation, not a contract. If you've got a bit of tarragon to throw in at the end, do it. If you want to swap the cream for crème fraîche for something sharper, that works too. We're only making dinner.