01 - In a microwave-safe mug (minimum 12 oz), whisk together the gluten-free flour, cocoa powder, sugar, baking powder, and salt.
02 - Add the milk, oil, and vanilla extract. Stir well until a smooth, lump-free batter forms.
03 - Fold in chocolate chips if desired.
04 - Microwave on high for 1 minute 30 seconds to 2 minutes, until the cake is set and springs back lightly when touched.
05 - Let cool for 1-2 minutes before serving. Top with whipped cream or berries if desired.