In a large bowl, whisk together all-purpose flour, whole-wheat flour, cocoa powder, baking powder, baking soda and salt until evenly blended.

In a blender or separate bowl, combine mashed ripe bananas, cottage cheese, eggs, vegetable oil, brown sugar, milk, melted butter and vanilla; blend until smooth.

Pour the wet mixture into the dry ingredients and gently fold together until just mixed, taking care not to overmix.

If using walnuts, fold them into the batter until evenly distributed.

Scoop batter into the prepared muffin cups, filling each about two-thirds full.

Bake until a toothpick inserted into the center comes out clean and tops are springy, watching for a rich chocolate rise.

Let muffins cool in the pan briefly then transfer to a wire rack to finish cooling before serving