In bowl; mix flour, cocoa, baking powder, sugar and salt.
Add milk and oil. Mix until fully incorporated.
Stir in coconut and walnuts.
Spray microwavable mug with non-stick. Transfer batter to mug.
Microwave on high for 60-90 seconds or until middle is done. Time will vary depending on microwave and mug size. Cake will rise and the top will no longer be fudgy once done.