Preheat the oven to 375. Line a muffin tin with parchment liners.
Scoop one cup of discard from your sourdough starter and set aside. Feed your starter as you would. Keep discard in the fridge until ready to use.
Prepare flax eggs and set aside to gel for 10 minutes. In the meantime, mash bananas in a large bowl and add olive oil, maple syrup, vanilla and whisk to combine.
Add flours, baking powder, baking soda and salt and mix thoroughly. Add in blueberries but reserve a few blueberries to garnish the tops of the muffins.
Use a spoon or ice-cream scoop to measure out 12 muffins. The batter will go almost to the top of each parchment liner.
Sprinkle turbinado if using and 3 blueberries onto each muffin. Bake for 23-25 minutes until a toothpick comes out clean and the tops are starting to turn a light golden brown.
*Macros are provided as an estimate for convenience. Your final numbers will vary depending on ingredient brands, substitutions, and how you portion the recipe.