Prep the pan and oven: Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or lightly grease with oil.
Mash the bananas: In a large bowl, mash the bananas with a fork until mostly smooth with small bits left.
You should have about 1 1/4 to 1 1/2 cups.
Whisk the wet ingredients: Add maple syrup, oil, Greek yogurt, eggs, and vanilla to the bananas. Whisk until well combined and creamy.
Mix the dry ingredients: In a separate bowl, whisk the white whole wheat flour, all-purpose flour, baking soda, baking powder, salt, and cinnamon.
Combine gently: Add the dry mixture to the wet. Stir with a spatula just until no dry spots remain. Do not overmix—a few small lumps are fine.
Add the chocolate chips: Fold in the dark chocolate chips (and nuts, if using).
Save a few chips to sprinkle on top for a bakery-style look.
Fill the cups: Divide the batter evenly among the 12 muffin cups. They should be about 3/4 full. Top with extra chips if you saved some.
Bake: Bake for 16–20 minutes, until the tops are set and a toothpick inserted in the center comes out clean or with a few moist crumbs (avoid the chocolate pockets when testing).
Cool: Let the muffins sit in the pan for 5 minutes, then transfer to a wire rack to cool completely.
This helps them set and keeps the texture light.