Blueberry Banana Muffins

Organic olive oil cooking spray for the muffin baking pans if you don't use paper or silicon muffin liners (tulip baking cup liners as shown in the pictures are also an option)

mashed very ripe bananas (about 2)

nonfat plain yogurt

honey

olive oil

vanilla extract

white whole-wheat flour

aluminum-free baking powder

baking soda

teaspoon salt

generous cup fresh or frozen blueberries

chopped walnuts, toasted (optional)