Place the pistachios in a food processor and pulse until coarsely chopped. With the motor running, drizzle in the 6 tablespoons of milk through the feed tube and process until a creamy paste forms, about 1 minute. You’ll still have small pieces of pistachios, and that’s okay.

Combine the remaining milk and cream in a medium saucepan set over medium heat. Cook until just barely simmering. Meanwhile, whisk together the egg yolks, sugar and salt in a medium bowl. Whisking constantly, gradually pour the warm milk mixture into the egg yolk mixture.

Pour the mixture back into the saucepan and cook over medium heat, stirring constantly and scraping the bottom, until the mixture is thick enough to coat the back of a spoon or spatula.

Pour the mixture through a strainer set over a medium bowl, preferably one with a pour spout. Allow to cool slightly, then whisk in the pistachio paste. Place a sheet of plastic wrap directly on the surface of the custard and refrigerate for at least 4 hours to chill completely.

Freeze in an ice cream maker according to manufacturer’s directions. When the ice cream is nearly done churning, melt the chocolate either in a glass bowl set over a saucepan of simmering water or in the microwave. Drizzle the melted chocolate into the custard in a slow, steady stream, avoiding the mixing blade as best you can. Transfer to a container with a tight-fitting lid, cover, and freeze until firm, about 4 hours.