Preheat oven to 450 F (230 C). Cut leeks in half lengthwise. Remove and discard the top tough green parts of leaves. Separate layers. Rinse well under cold running water. Then, slice into 1/2-inch (1-cm) lengths. Place on heavy foil. Sprinkle with 1 tablespoon water, salt and pepper. Seal and place in centre of oven for 10 minutes.
Meanwhile, whisk Dijon with maple syrup until almost blended. Stir in soy sauce. Place salmon in a foil-lined pan. Spoon half of syrup mixture over fish.
When leeks have baked 10 minutes, place fish in centre of oven beside leeks. Bake fish, uncovered, for 5 minutes. Then, spoon remaining sauce over top. Continue baking until fish flakes easily, about 5 minutes. Serve leeks alongside salmon.
A touch of maple syrup brings out the full seductive flavor of the salmon.