Recipe adapted from Alton Brown’s Chocolate Ice Cream.
1/2 cup unsweetened cocoa powder
3 cups half and half
1 cup heavy cream
8 egg yolks from large eggs
9 ounces sugar
2 teaspoons pure vanilla extract
Add cocoa powder and 1 cup of half and half to a saucepan over medium heat. Whisk to combine.
Add remaining half and half and heavy cream and bring mixture to a simmer, stirring occasionally. As soon as mixture simmers, remove from heat.
Whisk together the egg yolks in a mixing bowl until their color begins to lighten, then gradually add the sugar while whisking. Tempur the cream mixture into the eggs and sugar by adding small amounts slowly until a third of the cream mixture has been added. Pour in the remainder. Return the whole mixture to the saucepan and place over low heat.
Continue to cook, stirring frequently, until the mixture thickens and reaches 170 degrees. Pour mixture into a glass container and let sit at room temp for half an hour.
Stir in the vanilla extract, then place the mixture in the refrigerator for at least an hour. Then over and store in the fridge for 4 to 9 hours (temp should reach 40 degrees or below).
Pour into an ice cream maker and process. Serve as is for soft serve or freeze for 3 more hours for a denser ice cream.