Lightly grease a deep microwave-safe mug and set aside. In a bowl, mix protein powder, baking powder, sugar, flour, and Sipology's Hot Chocolate mix.
In another bowl, whisk egg and milk together and then add to dry ingredients. Mix to combine, then pour into mug.
Microwave for 60 seconds. Brownie should be cooked through but still gooey. If more time is needed, microwave in 10 second intervals. Remove from microwave and (optional) add a sprinkle of chocolate chips.