Combine milk, 1/4 cup sugar, and cardamom pods in a saucepan. Heat until steaming, about 4 minutes, then remove from heat and steep 20 minutes. Discard pods if used.

Whisk remaining 3/4 cup sugar, cocoa powder, and salt in a bowl. Whisk in egg yolks until thick. Slowly whisk in the warm milk, then return to saucepan. Cook over low heat, stirring, until custard coats the spoon, about 8 minutes to 170°F (77°C).

Off heat, stir in chopped chocolate until melted, then stir in heavy cream and rosewater. Cover surface with plastic wrap and chill at least 4 hours or overnight.

Churn chilled base in ice cream maker for 20 to 25 minutes until soft-serve consistency. In last minute, drizzle in date syrup and scatter pistachios.

Transfer to container, layering extra date syrup and pistachios if desired. Freeze at least 6 hours. Let soften 5 minutes before scooping.