Take 150 grams of unsalted, shelled pistachios and grind them into a fine powder using a food processor or grinder.
In a saucepan, heat 500 ml of full-fat milk and 250 ml of heavy cream over medium heat until it starts to steam. Do not let it boil.
In a separate bowl, whisk together 200 grams of granulated sugar and 6 egg yolks until the mixture becomes pale and creamy.
Slowly pour the warm milk and cream mixture into the egg yolk mixture, whisking continuously to avoid curdling.
Transfer the combined mixture back into the saucepan and cook over low heat, stirring constantly, until it reaches a custard-like consistency and coats the back of a spoon.
Remove the saucepan from heat and stir in the ground pistachios. Allow the mixture to cool to room temperature.
Once cooled, cover the mixture and refrigerate for at least 4 hours or overnight to chill thoroughly.
Pour the chilled mixture into an ice cream maker and churn according to the manufacturer's instructions.
Transfer the churned gelato to an airtight container and freeze for at least 4 hours or until firm.
Scoop the pistachio gelato into serving bowls or cones and enjoy!