Trim the livers of all connective tissue and cut away any green areas. In a glass or stainless steel bowl, combine the bay leaves, garlic, brandy and Marsala. Toss with the livers. Cover and refrigerate overnight.
Drain the livers, reserving the marinade. Pat them dry with paper towels. In a large heavy skillet, heat the 4 tablespoons butter over medium-high heat. Add the livers, the reserved bay leaves, and garlic, and toss 20 seconds or until the livers lose their red color. Pour in the marinade and boil about 2 minutes. The livers should be firm but still pink inside. Scoop them out of the pan with a slotted spoon and set aside. Continue boiling down the liquid until all of it has evaporated and the butter sputters. Add the 2 tablespoons of stock to the pan and scrape the contents over the livers. Cool to room temperature. Puree the livers in a food processor until smooth. Season aggressively with salt and freshly ground pepper.
Have a large bowl of ice handy. In a medium bowl, whip the 10 tablespoons butter with a portable beater at medium speed until fluffy. Gradually beat in the liver puree, then set the bowl over ice and continue beating at medium speed 8 to 10 minutes, or until the mixture has lightened in color and is very fluffy. Cover and refrigerate 1 to 2 hours.
To serve, bring the mousse close to room temperature. Spoon it into individual 3-inch ramekins or crocks, or mound it in a 3-cup terrine. Sprinkle generously with the shaved truffle. Accompany with bite-sized pieces of crusty bread.
In a large, heavy-bottomed saucepan, heat the oil over high heat until smoking. Add all the chicken parts and brown all over, stirring to avoid burning. Remove the chicken and reserve. Add the carrots, onions, and celery to the pot and cook until soft and browned. Return the chicken to the pot and add 3 quarts of water, the tomato paste, peppercorns, and parsley. Stir with a wooden spoon to dislodge the browned chicken and vegetables bits from the bottom of the pan. Bring almost to a boil, then reduce heat and cook at a low simmer until reduced by half, about 2 hours, occasionally skimming excess fat. Remove from heat, strain, and press on the solids with the bottom of a ladle to extract out all liquids. Stir the stock to facilitate cooling and set aside. Refrigerate stock in small containers for up to a week or freeze for up to a month.
Yield: 1 1/2 quarts