Place sugar, flour, cocoa powder and salt in a mug. Use a small whisk or fork, and stir until combined, and free of lumps. Stir in chocolate chips. Add oil, milk and vanilla, stir with a spoon or small rubber spatula until just combined (try not to over mix it).
Sprinkle a few additional chocolate chips over the top and cook in the microwave for 60-90 seconds, start checking it at 60. Time will vary a bit based on the microwave and the size of mug. Eat immediately with ice cream, whipped cream, powdered sugar, or berries.
