In a saucepan, combine the heavy cream, whole milk, and sugar. Heat over medium heat, stirring occasionally until the mixture is hot but not boiling.

In a separate bowl, whisk together the egg yolks. Slowly pour a small amount of the hot milk mixture into the yolks to temper them, stirring constantly to avoid curdling.

Gradually add the rest of the hot milk mixture into the yolks while continuously stirring.

Return the mixture to the saucepan and cook on low heat, stirring constantly until it thickens to a custard-like consistency (about 5-7 minutes). The mixture should coat the back of a spoon.

Remove from heat and stir in the vanilla extract.

Strain the custard through a fine mesh sieve into a clean bowl. Allow it to cool to room temperature before refrigerating for at least 2-3 hours or overnight.

In a saucepan, combine the unsweetened cocoa powder, sugar, and heavy cream over low heat.

Stir continuously until the mixture forms a smooth sauce. Allow it to cool for a few minutes.

Once both the vanilla base and chocolate sauce have cooled, pour the vanilla mixture into your ice cream maker and churn according to the manufacturer’s instructions (typically 20-25 minutes).

During the last few minutes of churning, slowly drizzle the chocolate sauce into the ice cream machine so it swirls through the vanilla base. This creates the beautiful chocolate ribbons in the ice cream.

Transfer the ice cream to a freezer-safe container, smoothing the top with a spatula.

Cover and freeze for at least 4-6 hours, or until it’s firm enough to scoop.