Preheat the oven to 350 degrees. Line a muffin tin with parchment paper liners.
Make the flax eggs: combine the ground flax seed and water in a small jar or cup and set aside.
In a large bowl, mix together the melted vegan buttery spread or coconut oil and sugar. Add the flax eggs, mashed bananas and vanilla, stirring until well blended.
Spoon the batter into the muffin tin, filling the cups 3/4 full. Bake for approximately 22-25 minutes or until a toothpick inserted in the center of a muffin comes out clean.
Let the muffins cool in the pan for a few minutes before moving to a wire rack to cool completely.
This recipe usually makes about 14 muffins, so if you have leftover batter, just repeat steps 5 and 6. Sometimes I just bake a few mini muffins at the same time to use up any excess batter. Mini muffins will need to bake for 16 minutes.
Store leftover muffins in an airtight container. They should stay fresh for 3-4 days.
You can freeze these if you like - just put into a freezer bag and store in the freezer for up to 3 months.