Preparation:

Remove dark green portion of the leek as well as a small portion of the root end. Cut the leek in half lengthwise. Clean by rinsing under cold water. Pat dry and thinly slice into half-moon shapes.

Remove shiitake stems and discard. Slice mushrooms and set aside. Dice potatoes into ½-inch chunks and set aside. Peel ginger and mince; set aside.

In a sauté pan on medium heat, sauté potatoes in 3 tbsp oil until just slightly tender, about 5 to 7 minutes. Add leeks and sweat for an additional 6 to 8 minutes. Remove leeks and potatoes from pan and reserve.

Season fish with salt and pepper and place on a hot grill; cook for 8 to 10 minutes (4 to 5 minutes per side).While fish is cooking, sauté mushrooms in a pan with 1 tablespoon canola oil on high heat for 2 minutes. Add ginger, reduce heat to medium, and cook 1 minute. Add leeks and potatoes back into the pan and heat for 2 minutes, or until potatoes are desired tenderness. 

Serve individual portions of fish over mushroom-potato mixture on four plates.