Place chocolate chips and oil in microwave-safe mug. Microwave on HIGH 20 seconds to melt chips; stir. Add milk, egg white and vanilla; whisk together with a fork until well blended. Add 3-1/2 tablespoons of the oats, the flour, sugar and cocoa powder. Whisk with fork to blend well, scraping sides and bottom of mug with rubber spatula. Sprinkle with remaining 1/2 tablespoon oats.
Microwave on HIGH 60 to 80 seconds until risen and just firm to the touch. Let stand 3 to 5 minutes before serving.