01 - Combine cottage cheese, egg, milk, and vanilla in a blender. Process until completely smooth and creamy.
02 - In a 10-12 oz microwave-safe mug, whisk together oat flour, protein powder, baking powder, cinnamon, sweetener, and salt until well incorporated.
03 - Pour the blended wet mixture into the mug. Stir vigorously until no dry patches remain and batter is uniform.
04 - Mix melted butter, cinnamon, and brown sugar in a small bowl. Dollop mixture over batter and gently swirl through using a knife or skewer.
05 - Cook on high power for 1 minute 30 seconds to 2 minutes. Cake is done when set and springs back lightly when touched. Begin checking at 90 seconds as microwave power varies.
06 - Whisk together softened cream cheese, milk, vanilla, and powdered sugar until smooth and drizzleable.
07 - Drizzle icing over warm mug cake. Enjoy immediately while warm for optimal texture.