01 -
In a microwave-safe mug with a capacity of at least 10 fluid ounces, thoroughly mix vanilla protein powder, oat flour, baking powder, ground cinnamon, granulated sweetener, and salt until evenly incorporated.
02 -
Stir milk, egg white, and vanilla extract into the dry mixture until a smooth batter without lumps is formed.
03 -
In a small bowl, blend melted butter, brown sugar, and ground cinnamon until the sugar is fully dissolved.
04 -
Drop spoonfuls of the cinnamon swirl mixture onto the batter in the mug, then use a toothpick or knife to gently swirl through the batter, producing a marbled pattern.
05 -
Microwave on high power for 60 to 90 seconds until the cake is set but still slightly moist in the center, taking care not to overcook.
06 -
While the cake cools briefly, beat together softened cream cheese, milk, powdered sweetener, and vanilla extract until smooth and spreadable.
07 -
Spread the cream cheese topping over the warm mug cake and enjoy immediately.