# Step-by-Step Directions:
01 - Place the Oreo cookies in a microwave-safe mug and crush thoroughly with a fork until finely crumbled.
02 - Add milk and mix until cookies are fully soaked, forming a thick paste.
03 - Stir in flour, sugar (if using), and baking powder until evenly incorporated.
04 - Incorporate the egg and vanilla extract (if using), mixing until the batter is smooth and uniform.
05 - Microwave on high for 1 minute 30 seconds. Verify doneness; the cake should be set but moist. If needed, microwave an additional 10 to 20 seconds.
06 - Allow to cool for 1 to 2 minutes before serving directly from the mug.