Place the cocoa powder together with 1 cup of the half-and-half into a medium saucepan over medium heat and whisk to combine. Add the remaining half-and-half and the heavy cream. Bring the mixture just to a simmer, stirring sometimes, and remove from the heat.

In a medium mixing bowl whisk the egg yolks until they lighten in color. Gradually add the sugar and whisk to combine. Temper the cream mixture into the eggs and sugar by gradually adding small amounts, until about 1/3 of the cream mixture has been added. Pour in the rest and return the whole mixture to the saucepan and place over low heat. Continue to cook, stirring often, until the mixture thickens barely and coats the back of a spoon and reaches 170 to 175°F.

Pour the mixture into a container and permit to sit at room temperature for 30 minutes. Stir in the vanilla extract. Place the mixture into the fridge and once it’s cool enough not to form condensation on the lid, cover and store for 4 to 8 hours or until the temperature reaches 40°F or below.

Pour into an ice cream maker and process according to the manufacturer’s directions. This should take about 25 to 35 minutes. Serve as is for soft serve or freeze for an additional 3 to 4 hours to allow the ice cream to harden.