In a medium saucepan, add the cocoa powder, espresso powder, and salt. Add 1 cup of half and half. In a 1-quart measuring cup or similar sized bowl, add the 2 cups half and half and the heavy whipping cream. Heat the saucepan with the dry mixture and the 1 cup half and half over medium heat and whisk to combine. Now add the remaining half and half and heavy cream. Bring the mixture just to a simmer, stirring occasionally. Remove from heat.
½ cup unsweetened cocoa powder, 1 tbsp espresso powder, ⅛ tsp sea salt, 1 cup half and half, 2 cups half and half, 1 cup heavy whipping cream
In a medium mixing bowl, mix the egg yolks with a hand-held mixer until they lighten in color. (You can use a large whisk to do this but the mixer makes it easier.) Add the sugar and continue to mix on high until fully incorporated.
8 large egg yolks, 1 cup granulated sugar
With the mixer still going, slowly add about ⅓ of the warm chocolate cream mixture. It's important to keep mixing (or stirring if you're not using a mixer) as the warm liquid is added. This process tempers the eggs, bringing them slowly up in temperature without curdling. Place the saucepan with the rest of the chocolate cream back on the burner, turn to low and slowly add the egg mixture to the pan, whisking or stirring as you add, again to prevent curdling.
Increase the heat to medium and cook, stirring frequently, until the mixture thickens slightly and reaches 170 to 175 degrees F. Wipe out the medium mixing bowl and place a fine mesh sieve over the bowl. Pour the entire custard mixture through the sieve into the bowl. This will remove any clumps or egg bits that may be in the custard.
Stir the vanilla extract into the custard. Let the mixture cool to room temperature (about an hour) and then cover and refrigerate until the mixture reaches 40 degrees F or lower.
2 tsps vanilla extract
Optional Chocolate Shavings: Before churning, finely shave your favorite chocolate bar with a sharp knife and break into small pieces if needed. Stir into the custard, then pour into the ice cream maker. Add as much or as little as you like (I used about 8 ounces bittersweet chocolate in the photos).
Pour the custard into an ice cream maker and process according to the manufacturer's instructions. This should take approximately 20-25 minutes. You may serve as soft serve ice cream at this point but I highly recommend freezing it overnight as the flavor is just going to get better and better.