Preheat an oven to 350 ℉ and line a 12 hole muffin tin with cupcake liners or grease with extra oil to prevent sticking.
In a small bowl, combine ground flax and water. Stir and let sit for 5 minutes to "gel."
Once the flax "eggs" have set for 5 minutes, pour them into your blender. Add the banana, pumpkin pure, vanilla, maple syrup/date syrup, oil, and vinegar. Blend until very smooth.
In a medium mixing bowl, combine flour, baking soda, baking powder, salt and pumpkin pie spice. Stir together. Pour in the pumpkin mixture from your blender into the bowl. Stir together and mix until well combined and batter has a smooth consistency.
Fold in chocolate chips, if using.
Portion the batter out into the prepared muffin tin and top with extra chocolate chips if desired.
Bake for 20-23 minutes or until a toothpick inserted into the center of a muffin comes out clean.
Let cool in pan for 5 minutes before transferring to a cooling rack. Let cool an additional 10 minutes before enjoying.
Enjoy! Let leftovers cool completely before storing them in an air-tight container in your fridge for up to 4 days or in freezer for a month or more.