2 cups heavy cream, divided
3 tbsp. Dutch-process cocoa powder
5 oz. bittersweet or semisweet chocolate, finely chopped
1 cup whole milk
¾ cup sugar
Pinch of salt
5 large egg yolks
½ tsp. vanilla extract
In a medium saucepan, combine 1 cup of the cream with the cocoa powder. Warm over medium-high heat, whisking to dissolve the cocoa. Bring the mixture to a boil, then reduce the heat to medium-low and let simmer for 30 seconds, whisking constantly. Remove the pan from the heat, mix in the chocolate and whisk until melted and smooth. Stir in the remaining 1 cup of cream. Transfer this mixture to a medium-large mixing bowl. Set a fine mesh sieve over the top.
In the same saucepan, combine the milk, sugar and salt and warm the mixture over medium-high heat. In a medium mixing bowl, whisk together the egg yolks. When the milk mixture is warm, gradually whisk into the egg yolks, beating constantly. Return the egg-milk mixture to the saucepan and continue heating over medium-high heat, stirring constantly and scraping the bottom of the pan with a spatula, until the mixture is slightly thickened and reads 170-175° F on an instant-read thermometer. Remove from the heat, pour through the mesh sieve into the chocolate-cream mixture and stir to blend. Stir in the vanilla extract.
Cover with plastic wrap and chill the mixture thoroughly in the refrigerator. (Alternatively to speed chilling, stir the mixture frequently over an ice bath.) Once the mixture is well chilled, freeze in an ice cream maker according to the manufacturer’s instructions. Store in an airtight container and freeze until ready to serve.