# Method:
01 - Place Oreo cookies in a microwave-safe mug and crush thoroughly with a fork until finely crumbled.
02 - Add milk to the crushed cookies and stir until fully soaked forming a thick paste.
03 - Stir in all-purpose flour, granulated sugar if using, and baking powder until well combined.
04 - Add the egg and vanilla extract if using, then mix until the batter is smooth and uniform.
05 - Microwave on high for 1 minute 30 seconds. Check that the cake is set but moist; if needed, heat for an additional 10 to 20 seconds.
06 - Let cool for 1 to 2 minutes before enjoying directly from the mug.