In a small bowl, mash the banana with a fork.
Add the melted fat (butter, oil or coconut oil), maple syrup, tahini, egg and vanilla. Mix well.
Sprinkle in the flour, baking soda, salt and fold in.
Add the chopped chocolate and fold.
Pour into a 10-12 ounce mug.Bake on high for 1 minute and 40 seconds.
Eat warm with a scoop of ice cream, drizzle of tahini or honey.