Instructions

1. Bring cream to a simmer in a medium heavy-bottomed saucepan over medium heat. Meanwhile, put egg yolks and sugar in a medium mixing bowl and whisk until thick, smooth, and pale yellow, about 5 minutes.
2. Slowly pour 1 cup of the hot cream into the yolk mixture, whisking constantly; then gradually add mixture back into the hot cream in the saucepan, stirring with a wooden spoon. Reduce heat to low and cook, stirring constantly, until custard is thick enough to coat the back of the spoon, about 10 minutes. Do not allow custard to boil (it will curdle).
3. Strain custard through a sieve into a medium bowl. Set aside to cool, then cover and refrigerate for at least 4 hours. Clean truffle, then shave and set aside a little more than half of it. Add vanilla to cold custard, then pour into an ice cream maker and process according to manufacturer's directions, adding truffle oil and shavings a few minutes before churning is completed. Serve gelato with a few shavings of remaining truffle over the top, if you like.