Step 1
In a medium bowl, whisk ¼ cup of the oil, vinegar, chives, parsley, chilli, Dijon mustard, wholegrain mustard and capers and season to taste with salt and freshly ground black pepper.
Step 2
Bring a large pot of salted water to a boil. Meanwhile, prepare a large bowl of iced water. Add the leeks to the boiling water and reduce the heat to a simmer. Simmer the leeks for about 10 mins or until they are tender (a small sharp knife should easily pierce them). Transfer the leeks to the iced water to chill completely. Drain the leeks well and cut in half lengthways. Remove the 2 outer layers from each piece of leek and cut the remaining leeks in half lengthways. Separate the layers to make leek ribbons. In a large bowl, toss the leek ribbons with 2 tbs of the dressing.
Step 3
Heat a large, heavy non-stick frying pan over medium-high heat. Add the remaining 1 tbs oil and swirl to coat the bottom of the pan. When the oil is hot, add the salmon fillets, skin-side down, and cook for 4 mins or until the skin is crisp and dark golden. Turn the salmon and cook for a further 1-2 mins or until the salmon is just opaque with a rosy centre. Set the salmon on a piece of kitchen paper to drain briefly.
Step 4
Divide the leeks among 4 dinner plates and top with a piece of salmon. Spoon the remaining vinaigrette around the plates and serve.