Preheat oven to 350°.
Place leeks side by side (they can overlap slightly) in baking dish.
Add butter and enough water to cover.
Bake 45 minutes; check dish frequently and add water and/or butter as necessary.
Turn leeks occasionally so that they will brown evenly.
Sprinkle with salt and pepper, bread crumbs, and Parmesan cheese and cook 5 to 15 more minutes until leeks are lightly browned and easily pierced with a knife.