Wash and drain lentils and place in a large saucepan with an onion studded with cloves, a carrot or two, and enough chicken broth to cover. Add salt, pepper, and a bay leaf or two. Simmer for about 45 minutes until the lentils are tender. Extract the bay leaves and purée with an immersion blender. Add grated truffle and a bit of heavy cream. Stir and serve, topped by an extra grating of truffle.