From My Bowl

0 Prep: Preheat the oven to 425F and generously grease a 12-muffin pan with vegan butter or oil. Combine the ground flax and water in a small bowl and mix well; let sit for at least 5 minutes, to thicken.
1 Dry Ingredients: Add the flour to a large mixing bowl, then add in the baking powder, baking soda, cinnamon, and salt. Whisk until combined, then form a well in the center of the bowl.
2 Wet Ingredients: Break the bananas into pieces and place in a smaller bowl. Mash the bananas well with a fork, mixing the mixture until it is mostly smooth and glossy.  Add the brown sugar, flax egg, milk, melted butter or oil, vanilla, and vinegar to the center of the bowl. Mix well, until a thick batter forms. Fold in the chocolate and walnuts, if using.
3 Divide the Batter: Use a large scoop or spoon to evenly divide the batter among the muffin tins, filling each tin level to the top. I like to sprinkle each muffin with a few extra chocolate chips, but that’s totally optional!
4 Bake: Bake in the middle rack of the oven for 7 minutes, then, without opening the oven, reduce the oven temperature for 350F. Bake for an additional 15 to 18 minutes, until the tops of the muffins are slightly golden.
5 Let Cool: Remove from the oven and set the muffin tin on a cooling rack; let the muffins rest for 5 minutes before using a knife to remove them from the muffin tin. Enjoy warm, or let cool completely on the wire rack before storing.
6 Storage: Muffins will keep in an airtight container at room temperature for up to 3 days. You can also freeze these banana muffins for up to two months, and defrost/reheat as necessary in a toaster oven. I do not recommend storing your muffins in the fridge as it makes their texture chewy.