In a 12 oz microwave-safe mug, whisk flour, granulated sugar, brown sugar, baking powder, and salt until evenly combined.
Add milk, vegetable oil, and vanilla; whisk until a smooth batter forms with no dry pockets along the bottom.
Fold in most of the chocolate chips, then sprinkle a few on top.
Microwave on High for 1 minute 30 seconds to 2 minutes, or until the top looks set and springs back lightly. If the center is still wet, continue in 10-second bursts.
Let stand 1 minute to finish setting. Enjoy warm straight from the mug.
Notes
Use a wide, microwave-safe mug for best rise. Microwave strengths vary; start low and add time as needed to avoid drying out. For extra richness, top with a scoop of vanilla ice cream or a drizzle of chocolate syrup.