Cut into a fillet and remove the skin. Cut the fillet into 12 nice pieces.
Clean the leeks in lots of cold water to get rid of all the dirt. Divide them into 12 pieces, each about 5 cm long.
Peel the onion and chop finely with the capers. Mix them together with the oil, vinegar, mustard, honey, salt and pepper to make a nice thick vinaigrette.
Boil the leeks tender in lightly salted water. Remove them from the water and place them directly into the vinaigrette with a little of the cooking water (leek bouillon), so they absorb the vinaigrette and all the flavor.
Fry the halibut in a pan for about 1-2 minutes on each side, depending on the thickness. Season with salt and pepper. Serve with leeks and compote.