Season halibut lightly with salt, pepper and lime zest and set aside. Blanch chard leaves in lightly salted water for 5 to 10 seconds until softened and then immediately plunge into ice water to stop cooking and set color. Pat dry and wrap halibut pieces completely with leaves.
To serve: Add mushrooms, scallions and olive oil to an oven-proof saute pan large enough to hold fish in one layer. Saute mushroom mixture until its just beginning to color. Place wrapped fish on top of mushroom mixture, add the wine and stock and cover. Finish cooking fish on top of stove over moderate heat or in a preheated 400 degree oven for 10 to 12 minutes or until fish is cooked through. With a spatula, lift fish and its mushroom bed and place attractively on warm plates. Pour sauce around and garnish with cilantro sprigs and deep fried leeks on top of wrapped fish.