Cover cheese with the milk and let stand for about three hours. Drain and reserve 1/4 cup of the milk. Place cheese in the top of a double boiler with a little salt and place over simmering water. Stir constantly with a whisk until melted and smooth. Heat the reserved milk and mix in the egg yolks and butter. Stir rapidly into the melted cheese until the mixture is smooth and creamy. Pour into a heated serving dish, shave the truffle thinly over the top and serve while it's still very hot.