Slice leeks in half lengthwise, loosen the layers and run them under cold water to wash out any sand or dirt. Cut the halves into 1/2-inch thick slices and place them in a saucepan of salted water. Bring to a boil, then simmer until leeks are fully tender – about 6 minutes. Drain and place leek slices in a blender with the basil leaves and butter. Purée until very smooth and return to the saucepan to keep warm, and season well with salt and freshly ground white pepper.
Next, place the sun-dried tomatoes, olives, capers, herbs, and olive oil in a small processor or spice grinder; purée until it forms a chunky paste.
Divide and spread the paste among the tops of the two salmon fillets, pressing it gently to adhere.
Place salmon on an oiled baking sheet and roast for 8-10 minutes, depending on thickness and your preference. (Our fillets we about 1 inch thick, and were perfect after 9 minutes.)
To serve, spoon some of the leek-basil purée on a dinner plate and top with salmon. Sprinkle with parsley.