Miscellaneous with chicken

2 tablespoons unsalted butter , plus extra for the baking dish 2 cups polenta or 2 cups coarsely ground yellow cornmeal 1 quart water or 1 quart chicken stock[...]

6 medium potatoes , peeled and thinly sliced 1 onion , thinly sliced 3 tablespoons butter or 3 tablespoons margarine 1/4 cup chopped onion 3 tablespoons[...]

5 lb Long Island duck - (to 5 1/2 lbs), thawed     if frzn 4 1/2 quart Duck stock saved from a prior roasting     (or possibly Basic Chicken Stock, or[...]

4 x dry black mushrooms 1/2 bn spinach - (abt 6 ounce) 1/2 lb hard-textured 3/4"-thk white fish fillets     (such as cod, halibut, or possibly sea bass)[...]