In a medium saucepan, combine the half & half, Dutch-process cocoa powder, black cocoa powder, and espresso powder if using. Heat gently over medium-low heat, whisking continuously until the mixture is smooth and glossy, about 4-5 minutes.

Once the cocoa mixture is warm, stir in the chopped dark chocolate. Mix continuously until the chocolate melts completely and integrates into the cocoa blend, creating a silky texture, about 2-3 minutes.

To the chocolate mixture, whisk in the allulose, nonfat dry milk powder, and a pinch of sea salt. Then, pour in the heavy cream, vanilla extract, and vodka if using. Stir gently until the mixture is homogenous and creamy, which should take another 2-3 minutes.

Pour the ice cream base into a container and cover it with a lid or plastic wrap. Transfer it to the refrigerator and chill for at least 4 hours, though overnight is recommended for optimal flavor development.

Once chilled, pour the mixture into your ice cream maker and churn according to the manufacturer's instructions. Expect the mixture to thicken significantly, typically taking around 20-30 minutes.

Transfer the soft ice cream to a freezer-safe container, smooth the top with a spatula, and seal it with an airtight lid. Freeze for 2-4 hours until it reaches your desired firmness.