Chicken Liver Mousse with Truffles: Spuma di Fegati con Tartufo

Name: Chicken Liver Mousse with Truffles: Spuma di Fegati con Tartufo
Ingredients: 8 ounces chicken livers; 8 ounces duck livers; 4 bay leaves; 1 clove garlic, lightly crushed; 1 tablespoon brandy; 3/4 cup dry Marsala; 4 tablespoons plus 10 tablespoons unsalted butter; 2 tablespoons chicken stock, recipe follows; Salt and pepper; 1 small fresh white or black truffle, shaved into very thin slices with a truffle slicer; Good quality crusty bread; 2 tablespoons extra-virgin olive oil; 3 1/2 pounds chicken wings, backs, and bones; 3 carrots, coarsely chopped; 2 onions, coarsely chopped; 4 ribs celery, coarsely chopped; 2 tablespoons tomato paste; 1 tablespoon black peppercorns; 1 bunch parsley stems