01 - In a microwave-safe mug (minimum 12 ounces), whisk together the gluten-free flour, cocoa powder, sugar, baking powder, and salt until uniformly blended.
02 - Pour in the milk, vegetable oil, and vanilla extract. Mix vigorously with a fork until a smooth batter forms, ensuring to scrape the bottom and sides of the mug.
03 - Gently fold in the chocolate chips if desired.
04 - Microwave on high power for 1 minute. The cake should appear set but maintain a moist center. If necessary, continue microwaving in 10-second increments until cooked through, avoiding overcooking.
05 - Allow the cake to rest for 1 to 2 minutes to slightly cool and set before serving directly from the mug.