1½ cups milk
1½ cups heavy cream
1 cup sugar
½ vanilla bean
Mix the milk, cream, and sugar in a saucepan. Heat over medium heat, stirring continuously, until the sugar is dissolved and bubbles form at the edge. Remove from the heat and add the vanilla, scraping the seeds into the pan. Let stand 30 minutes, then remove the vanilla bean pod. Refrigerate overnight, then process in an ice cream freezer following the manufacturer's instructions. Place in the refrigerator freezer until firm.
If you can't get Tahitian vanilla beans, or don't want the seeds in your gelato, use Tahitian vanilla extract. Or you could substitute any vanilla bean or even vanilla paste. If you use vanilla paste, I suggest 1½ teaspoons.