In a microwave safe mug, mix in all the dry ingredients.
Add the wet ingredients and whisk until combined.
Add the chopped chocolate on top.
Microwave for 50-70 seconds, depending on the power of your microwave. I like the brownie to be extra fudgy and slightly underdone, so I cooked mine to 60 seconds. Allow brownie to cool a few minutes before eating. Its is best eaten warm.