Combine the sugar, cocoa, cornstarch, salt, spices, and egg (or yolks) together in a saucepan. Mix to combine.
Over low heat, slowly add the milk while whisking.
Continue to whisk over low heat until mixture comes to a boil.
Boil for 1-2 minutes.
Remove from heat and add butter and vanilla, continue whisking until butter is fully melted and mixed in.
Pour into small ramekins and chill. If you wish to prevent a skin from forming, press a layer of plastic wrap directly onto the surface of the pudding.
Garnish with a sprinkle of chili powder.
Recipe by The Kitchen Paper at http://c02.ddd.mwp.accessdomain.com/mexican-hot-chocolate-pudding/