Prepare an ice bath set up- you will need a fine mesh strainer set over a medium bowl which is placed in a large bowl. The large bowl will have about a cup of ice in it with enough water to barely float ice. The medium bowl will sit in the ice water to help cool the mixture quicker in the last steps of making the custard. If you don't have bowls that will work use a bowl set in a large roasting pan with ice in it or you can make the ice bath in your sink.

In a medium saucepan, thoroughly whisk together 1 cup of the heavy cream and the cocoa powder. Heat mixture until it boils, whisking occasionally to make sure it is well combined. Once at a boil, reduce the heat and simmer for 30 seconds while whisking constantly. Remove pan from the heat and stir in chopped chocolate until well combined. Stir in remaining cup of heavy cream. Pour this mixture into the medium bowl, scraping pan well, so you can reuse it. Set the strainer on top of the bowl with the chocolate mixture in it.

In the same (now empty) saucepan, add the milk, sugar and salt and warm over med to med/low heat until steam appears and milk is warm (if you have an instant read thermometer, warm mixture until it reaches about 175 degrees). While milk mixture is warming, in medium bowl whisk together egg yolks until smooth. Once the milk mixture is warm enough, slowly stream the warm milk mixture into the egg yolks while whisking constantly (you don't want scrambled eggs so keep mixture moving and add milk slowly).

Pour the egg/milk mixture back into the saucepan. Heat, while stirring constantly with a wooden spoon or heat proof spatula, until the mixture thickens enough to coat the back of the spatula ( you will be able to leave a finger trail that stays in the coating on the spatula, this will be about 180 to 185 degrees on an instant read thermometer). Do not allow mixture to boil because it may curdle.

Pour mixture through the strainer into the chocolate mixture then stir until combined. Add vanilla extract.

Place bowl into ice bath and stir occasionally until mixture cools.

Cover and place in the refrigerator until completely chilled. I find 8 hours or overnight yields the best results.

Freeze in ice cream maker according to the manufacturers instructions.