1. Preheat the oven to 180˚C, gas mark 4. Put the leeks in a roasting tin and pour over the wine, 50ml olive oil and 150ml water. Cover with foil and bake for 35-45 minutes; cool slightly.
2. Boil the whole egg for 9 minutes. Cool, peel and finely chop. Beat the egg yolk and mustard; slowly whisk in 125ml olive oil. Whisk in the vinegar and 1 tbsp water; season. Stir in the egg, capers and ½ the parsley.
3. Spread the leeks over a platter. Splash with a little of the cooking liquid, then the gribiche sauce and the remaining parsley.
This recipe first appeared in Waitrose Kitchen magazine. myWaitrose members can download the Waitrose Kitchen app edition for FREE. Find out more.