01 -
Preheat your oven to 375°F (190°C).
02 -
In a large bowl, stir together the dry ingredients (flour, baking powder, baking soda, cinnamon, and salt). If using rolled oats instead of flour, blend them in a food processor until they become a fine flour before mixing with the other dry ingredients.
03 -
Add all the wet ingredients (Greek yogurt, milk, ripe bananas, eggs, baby spinach, and vanilla extract) into a blender and blend until completely smooth and the spinach is fully incorporated.
04 -
Pour the wet ingredients into the bowl with the dry ingredients. Using a spatula (not a whisk), gently fold everything together just until all the flour is moistened. Be careful not to overmix - this will keep your muffins light and fluffy.
05 -
If using, gently fold in the grated sweet potatoes or carrots (make sure they're squeezed dry), chopped walnuts, and/or sweetener of choice.
06 -
Divide the batter evenly among 12 muffin cups in a greased, lined, or silicone muffin pan.
07 -
Bake in the preheated oven for 20-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
08 -
Allow the muffins to cool in the pan for at least 5 minutes before transferring them to a wire cooling rack to cool completely.