In a microwave-safe bowl, combine chocolate and cream, microwave on high for 30 seconds, stir, heat 30 seconds more, and stir again. Repeat in 10-second bursts, stirring each time, until there are no lumps of unmelted chocolate remaining, about 70 seconds total. Whisk to combine chocolate and cream.
In a separate medium-size microwave-safe bowl, combine sugar, skim milk powder, and cocoa powder, mix. Add 1/3 to 1/2 cup milk. You want to add just enough milk to make the mixture wet. If you rub it between your fingers, the mixture will feel gritty because of the sugar.
Heat chocolate mixture in microwave for 60 seconds on high, stir, then repeat in 20-second bursts, stirring after each time, until sugar is dissolved. Whisk cream mixture into chocolate.
Pour in remaining milk and whisk until well combined. Cover and refrigerate for at least 3 hours or until completely chilled.
Pour mixture into an ice cream machine and churn according to manufacturers’ directions, about 30 minutes.
Freeze until firm, about 3 hours.