Preheat oven to 350 degrees F. Line a muffin pan or spray with oil.
In a medium bowl, make flax egg by combining the ground flaxseed with water. Mix and set aside for 5 minutes to thicken.
In a liquid measuring cup or bowl, combine almond milk (or any non-dairy milk) with vinegar. Set aside for 5 minutes. This is your vegan buttermilk!
In a large bowl, combine the flour, baking soda, and cinnamon. Mix until well combined.
In the bowl with the flax egg, add the coconut sugar and vanilla extract. Whisk until it is well combined. Then add the buttermilk mixture and melted coconut oil. Whisk again until combined.
Add wet ingredients to the dry. Mix with a spatula until just combined. Careful not to overmix! Fold in the mangoes.
Fill each muffin mold until almost full. This will ensure big, fluffy muffins. Bake for 18-20 minutes until golden and when a toothpick comes out clean. Allow the muffins to cool in the pan for 5 minutes. Then transfer the muffins to a cooling rack to cool completely.
Enjoy!