This is the original recipe from Good Eats, Churn Baby Churn II:
3 cups half and half
1 cup heavy cream
1 1/2 ounces Dutch-processed cocoa powder
8 large egg yolks
9 ounces white sugar
2 teaspoons vanilla (for the Thin Mint ice cream, I only used 1 tsp of the mint extract)
1 sleeve of Thin Mints crushed (if making thin mint ice cream)
Whisk 1 cup of half and half with the cocoa in a saucepan. Combine with remaining half and half and heavy cream. Bring to a simmer over medium heat, stirring occasionally. Remove from heat and set aside.
Whisk egg yolks in large mixing bowl until they lighten in color. Gradually add sugar until smooth.
Slowly ladle one third of hot cocoa mixture into the yolk mixture whisking constantly (which is why I use a mixer) to temper eggs. Return this mixture to the saucepan with remaining cocoa mixture. Cook over low heat, stirring frequently until the custard thickens slightly & coats the back of a spoon.
Add vanilla (or mint), and cool to room temp (about 30 minutes). Cover and refrigerate until temp drops below 40 degrees (overnight works best).
Pour into prepped ice cream maker and process. About 5 minutes before end time, sprinkle in crushed Thin Mints. Serve with whole or crushed Thin Mints. Enjoy!!!