In a medium saucepan, combine milk, cream, and half the sugar. Scrape vanilla bean seeds into the milk and add the pod. Heat over medium until steaming, not boiling.
In a bowl, whisk egg yolks with remaining sugar and salt until pale and thick.
Slowly pour hot milk mixture into yolks, whisking constantly. Return mixture to saucepan.
Cook over low heat, stirring constantly with a wooden spoon, until custard thickens and coats the back of the spoon (about 8-10 minutes). Do not boil.
Strain custard through a fine-mesh sieve into a bowl. Discard vanilla pod. Stir in vanilla extract if using. Cool to room temperature, then refrigerate until thoroughly chilled (at least 4 hours or overnight).
Churn in an ice cream maker according to manufacturer's instructions until soft-serve consistency.
Transfer gelato to a container and freeze for at least 2 hours until firm.
Scoop gelato into waffle cones and serve immediately.
Tips
For best texture, let gelato soften at room temperature for 5 minutes before scooping.
Store leftover gelato in an airtight container in the freezer for up to 2 weeks.
To make chocolate gelato, add 1/2 cup unsweetened cocoa powder with the milk.