Whisk the sugar, cocoa powder, baking powder ,and salt together in a medium bowl. Then, in a second bowl, whisk together the egg, oil ,and vanilla.
Evenly divide the chocolate chips and milk between two 10-ounce microwave-safe mugs. Nuke on high for 30 seconds. Meanwhile, stir the egg mixture into the sugar mixture to thoroughly combine.
Carefully extract the mugs and whisk the chocolate-milk mixture until smooth. Then divide the batter between the mugs and stir to combineI usually use a fork for this..
Park the mugs on a paper plate or paper towel in the center of the microwave carrousel, and just let them sit therefor 3 minutes. (Don’t skip this step — it’s giving the baking powder a head start!) Then, microwave on high for 1 minute and 45 seconds. Be sure to gaze in wonder as the batter rises soufflé-like right up out of the mug only to sink safely back into the confines of the mug moments before the final bell.
Carefully remove the mugs and either turn out into a bowl to devour with ice cream or — as I do because I have the discipline to wait — cool almost to room temp and devour out of the mug with whipped cream.