Leek and Potato salad with classic French vinaigrette

Name: Leek and Potato salad with classic French vinaigrette
Prep time: 10 mins
Cook time: 40 mins
Yield: Serves 6
Ingredients: 3tbsp Dijon mustard; 11/2tbsp red-wine vinegar; 150ml sunflower oil; 50ml extra-virgin olive oil, plus extra for drizzling; 11/2tbsp chopped tarragon; 1tsp coriander seeds, coarsely ground in a pestle and mortar; 2tbsp chopped chives; 6 medium or 12 small leeks; 2 bay leaves; 10 small waxy salad potatoes; 2 medium eggs, at room temperature