In a medium saucepan, combine the milk and cream. Place over medium-low heat and cook, stirring occasional so a skin doesn't form. You want the temperature to reach 170°F. Turn off heat and whisk in the cocoa powder and chopped chocolate until the mixture is completely smooth.
While heating milk/cream mixture, whisk egg yolks in medium bowl. Gradually add sugar, salt and xanthan gum and whisk until mixture is thick and pale yellow.
Temper egg yolks by slowly pouring 1 cup hot milk mixture, whisking constantly. Return egg yolk mixture to sauce pan and place over low heat. Cook, stirring frequently with a wooden spoon until the custard reaches a temperature of 185°F. Pour the mixture through a fine-mesh strainer into a clean bowl and cool to room temperature, stirring every 5 minutes. Once room temperature, cover and place in refrigerator for at least 4 hours.
Remove the custard from the refrigerator and stir in the vanilla extract. Pour the mixture into an ice cream machine and churn for about 20 minutes (follow your ice cream maker directions). Transfer gelato to airtight container and freeze until solid, about 2 hours.
Use the best ingredients – when making gelato you want to use the best ingredients possible so use free-range eggs and organic milk and cream. Also use high quality products when it comes to added flavorings like vanilla or chocolate. Never use imitation vanilla.
Add extract at right time – if you add an extract or alcohol while the custard is too hot, you won’t get the actual flavor as it will cook out slightly. Just wait until right before you pour the custard into the ice cream maker to add it.
Chill the custard – you don’t necessarily need to chill the custard overnight, but you want to chill until it is as cold as possible.
Use frozen bowl – make sure your ice cream bowl has been frozen for at least 24 hours, otherwise you aren’t giving the gelato a great chance of freeze.
Start ice cream motor first – do not pour the custard in the frozen bowl before starting the ice cream maker. It will start freezing upon contact. You want the motor running and slowly pour the custard in.
Don’t overchurn – always error on the side of caution when it comes to churning your homemade gelato. You do not want it to be hard. Remember it will continue to freeze once you place in the freezer.
Keep it creamy – homemade gelato can turn hard as we don’t add preservatives, however xanthan gum or a couple tablespoon of vodka will help keep it creamy.