01 - In a microwave-safe mug (at least 12 oz), whisk together the gluten-free flour blend, cocoa powder, sugar, baking powder, and salt until evenly distributed.
02 - Pour in the milk, oil, and vanilla extract. Stir thoroughly until a smooth, lump-free batter forms, scraping the sides and bottom of the mug.
03 - Fold in chocolate chips if desired, distributing them evenly throughout the batter.
04 - Microwave on high for 1 minute 30 seconds to 2 minutes, until the cake is set and springs back lightly when touched. Cooking times may vary depending on microwave wattage.
05 - Allow the cake to cool for 1 to 2 minutes. Top with whipped cream or fresh berries if desired, and serve warm.