Stud the peeled onion with the whole cloves. Make a small "bouquet garni" by tying the peppercorns, parsley, thyme and bay leaf in a small cheesecloth pouch.
Preheat oven to 350° F.
Sprinkle rabbit pieces with salt and pepper and sauté in the butter until brown on all sides. Place in a 3 quart casserole. Add salt, "bouquet garni" and studded onion, followed by the lemon juice, port and stock or boullion. Cover and bake for 1 1/2 hours. Ten minutes before it's done, remove the cheesecloth bag. The pan juices can be thickened to make a gravy.