Saute the mushrooms in butter until the juices run, then season with salt and pepper and nutmeg. Reserve.
Remove the sinews from the livers and slice. In a large bowl combine all the ground meats, sausage, livers, onion, garlic, and juniper berries. Add the allspice and thyme leaves. Season with salt and pepper. Beat the eggs and add to the mixture together with the mushrooms. Mix with your hands thoroughly.
Oil a roasting pan and place all the mixture in it, molding it into an oval shape. Adorn with the bacon slices, criss-crossed, tucking the ends under the meat. Strew some bay leaves and branches of rosemary on the top and sides. Cook in the preheated oven for 15 minutes, then lower the heat to 350 degrees and cook for 1 1/2 hours.
When cooked, there will be lots of lovely juices in the bottom of the pan. Save them to flavor soup, stocks, or eggs. Remove the loaf and place on a serving dish. Serve hot or cold with a tomato sauce.
For children, you might like to turn it into a hedgehog by pressing almonds into the meat to create prickles and placing 3 olives to form eyes and a nose. This should be done before the meat goes into the oven.