Coffee and Chocolate Mug Cake

1.In a microwave-safe mug (about 12-14 oz), whisk together the all-purpose flour, cornstarch, sugar, baking powder, and salt until well combined and no lumps remain.

2.Add the milk, vegetable oil, cold brewed coffee, chocolate syrup, and vanilla extract (if using) to the dry ingredients. Stir well with a fork or small whisk until the batter is smooth and all ingredients are incorporated. Be careful not to overmix.

3.If desired, spoon 1 tablespoon of dulce de leche or cajeta into the center of the batter. Gently push it down slightly, but do not stir it in.

4.Microwave the mug cake on high for 60-90 seconds. Cooking time can vary depending on your microwave's wattage. Start with 60 seconds and then microwave in 10-second increments until the cake is set and springs back slightly when touched. Be careful not to overcook, as it can become dry.

5.Carefully remove the mug from the microwave. Let it cool for a minute or two before serving.

6.Serve warm, optionally topped with whipped cream or ice cream, and garnished with chocolate shavings or crushed cookies.