In a bowl, stir together the mashed bananas, coconut oil, honey, egg, and vanilla until combined. Add the flour, baking soda, cinnamon, and salt, mix until just combined. Fold in the chocolate chunks. Pour the batter into a (10-12 ounce) microwave-safe mug. Microwave on full power for 1 minute and 35 seconds to 2 minutes (I always do 1 minute 35 seconds, but it's better to under "bake"). Eat warm with a smear of butter and a drizzle of honey (you should do this!). Enjoy!