Preheat oven to 425 °F (218°C). Line a 12-count muffin pan with cupcake liners and set aside.
Prepare your flax egg: Stir 1 tbsp ground flax meal + 3 tbsp of warm water in a bowl. Set aside for 5-10 mins.
Whisk dry ingredients: Whisk together flour, baking soda, baking powder, salt, cinnamon, and nutmeg together in a medium bowl. Set aside.
Prepare wet ingredients: In a larger bowl, mash the bananas. Beat or whisk in brown sugar, vanilla extract, melted vegan butter, milk, and flax egg.
Pour the dry ingredients into the wet ingredients. If you are adding nuts, do so now. Then, using a whisk or spatula, whisk or stir the batter until combined. Do NOT overmix. 10-12 stirs is all you need. The batter will be thick - "spoonable" not pourable.
Spoon the muffin batter into the cupcake liners. Fill them to the top. Bake the muffins at 425°F for 5 minutes. *
After 5 minutes, reduce oven to 350°F (177°C) and let muffins bake for an additional 16-18 minutes, or until a toothpick comes out clean. Remove the muffins from the oven and allow them to cool for 5-10 minutes. Then, place them on a wire rack to allow them to cool completely.
Muffins will keep for a few days at room temperature or up to 1 week in the fridge. They can be frozen for up to 3 months in a resealable bag.
'Spooned & leveled' flour: This means to spoon the flour into a measuring cup and then level it off. You can use the back of a knife to level the flour. It's a wonderful tip to make sure you're using the right amount of flour.
Baking at a higher temperature: The initial high heat (425°F) creates a burst of steam that lifts the top of the muffin. This gives your muffins high domes.
Dairy-free milk: I prefer to use cashew milk as it's thicker and creamier than almond or soy milk - However, any dairy-free milk will add moisture to the muffins.