Heat Milk and Cream: In a saucepan, combine milk, heavy cream, and cocoa powder. Warm over medium heat until hot but not boiling.
Prepare Egg Mixture: In a separate bowl, whisk together egg yolks and sugar. Slowly temper the yolks by gradually adding the hot milk mixture while whisking constantly.
Cook Custard: Return the mixture to the saucepan. Cook over low heat, stirring constantly, until it thickens slightly and coats the back of a spoon.
Cool: Remove from heat and stir in vanilla extract. Cool completely in the refrigerator.
Churn: Pour the custard into an ice cream maker and churn according to the manufacturer’s instructions.
Add Mix-Ins: Gently fold in mini marshmallows and chopped nuts.
Freeze: Transfer to a freezer-safe container and freeze until firm, about 4 hours.
Serving and Storage Tips:
