To fry the leek
Halve the leek crosswise, tie the ends with kitchen twine. Heat a dash of oil in a frying pan. Fry the leek in batches for approx. 2 mins. on each side, remove and season.
To braise the leek
Return the leek to the pan, pour in the wine and stock. Cover and braise over a medium heat for approx. 30 mins.
Heat the oil in a pan, briefly cook the quinoa. Pour in the water, season with salt, bring to the boil, cover and simmer over a low heat for approx. 20 mins. until just soft. Mix in the diced vegetables.
Serve the leek with the quinoa. Combine the mustard, vinegar and oil with the cooking juices, season. Drizzle the vinaigrette over the top, garnish with the tarragon and nuts.