Place sugar (3 tbsp), flour (3 tbsp), cocoa powder (1 ½ tbsp) and salt (pinch) in a mug. Use a small whisk or fork, and stir until combined, and free of lumps. Stir in chocolate chips (2 tbsp). Add melted butter (1 ½ tbsp), milk (3 tbsp), and vanilla (¼ tsp), stir with a spoon 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 seconds. Check to see if it is done (no raw batter, fudgy chocolate chips are ok). If necessary, continue cooking in 10 second increments.