Preheat the oven to 350°F and lightly grease a 12-slot muffin pan
In a small bowl, prepare the flax egg by combining 1 tbsp ground flax with 2.5 tbsp water. Allow it to sit for 10 minutes.
In a bowl, combine dry ingredients: flour, baking soda and powder, allspice and cinnamon, coconut sugar and a pinch of salt.
Separately, prepare the wet ingredients: 2 bananas mashed with a fork, oil or vegan butter, vanilla extract and flax egg.
Mix the wet ingredients together with the dry ingredients until well combined. The batter will be pretty thick. Add 1/4 cup of plant milk or water as necessary. Add 1-2 tbsp more plant milk if necessary but it's ok if the batter is a little thick, that's how it's supposed to be.
Evenly distribute the batter in the muffin tray. You may optionally add a few chocolate chips on top.
Fold in the chocolate chips and optional nuts.
Bake in the oven for 20 minutes. Using the toothpick test, check to see if the toothpick or fork comes out clean. If not, bake for an additional few minutes.
Allow to cool for 5-10 minutes before carefully removing.