I could not find a recipe today for the life of me. BUT, I found the most wonderful picture of frozen custard with melted, tempered dark chocolate just oozing down all over it.
The website I found it on was all in Chinese, since I do not know Chinese, I can't investigate it further. Boy, do I wish I knew this recipe, although, if you have a simple frozen custard recipe, temper chocolate and drizzle it over the custard. Just got to do it quick, so it doesn't melt before serving....check it out.