Heat oven to 400° F. In a large saucepan, over medium-high heat, fry the bacon until almost crisp. Spoon off and discard all but 1 tablespoon of the drippings.
Add the leeks and cook, stirring occasionally, until tender, about 3 minutes.
Add the potatoes, corn, wine, cream, 1 teaspoon salt, and ½ teaspoon pepper. Bring to a boil.
Transfer to an 8-by-11-inch baking dish or shallow 2-quart casserole. Nestle the cod pieces in the potato mixture. Top with the crackers. Cover loosely with foil.
Bake until the fish is cooked through, about 20 minutes.