Clean the truffles carefully with a soft brush. Chop large truffles into pieces about ¼ inch, and split the smaller ones to release the flavor.
In a saucepan, bring the beef broth to a boil, add the truffles, and immediately reduce to a simmer. Cook the truffles for no more than about 20 seconds.
Pour the broth through a sieve into a bowl and set the broth and the truffle pieces aside.
Grease a 5-cup mold or enough small crocks to hold 5 cups.
Combine the chicken livers, onion, apple, reserved broth, and shallots in a medium saucepan and bring to a boil over medium heat. Reduce the heat, cover, and simmer for 5 minutes.
Stir the lemon juice, water and gelatin together in a bowl, making certain that the mixture is well blended and the gelatin is dissolved.
Pour into the liver mixture and mix thoroughly.
Remove from the heat and add the butter a few pieces as a time. Blend well after each addition.
Stir in the remaining ingredients and allow to cool for 15 minutes.
Transfer the mixture to a blender or a processor and pure until not quite smooth. Let stand 10 minutes.
Pour a third of the mixture into the mold, then layer 1/3 of the truffle pieces.
Pour in another third of the pate, and again layer with truffle pieces.
Repeat a final time.
Cover and chill for at least 8 hours. The flavor will improve if left for 24 to 48 hours.