Add egg to regular size coffree mug and whisk
Whisk in almond milk, honey, and lemon juice
Add banana and mash and stir until everything is thoroughly mixed
Add almond flour, coconut flour, baking soda, and dash of salt
Whisk until everything is combined
Stir in walnuts if using
Microwave on high for 90 seconds - muffin will puff up over the rim of the mug, but it shouldn't actually spill over
Allow to cool for a minute or two before eating