Heat oven to 350°F. Grease a 9×5-inch loaf pan and line with a parchment sling.
Whisk flour, baking soda, baking powder, salt, and cinnamon in a medium bowl.
Mash bananas in a large bowl until mostly smooth.
Stir in granulated sugar, brown sugar, melted butter, yogurt, beaten eggs, and vanilla until combined.
Fold the dry mixture into the banana mixture just until no flour streaks remain.
Gently fold in chocolate chips and walnuts, reserving a spoonful of chips for topping.
Scrape batter into the pan and smooth the top. Sprinkle with reserved chips.
Bake 50–60 minutes, until a tester comes out with a few moist crumbs. Tent with foil if browning early.
Cool 10 minutes in the pan, then lift out and cool completely on a rack before slicing.