Preheat the oven to 325 degrees F.
Butter a 9 x 5 x 3-inch loaf pan.
In a small bowl, mash the bananas with a fork. Stir in the whole milk and ground cinnamon. Set aside.
In a medium mixing bowl, whisk together the all-purpose flour, baking powder, baking soda and salt. Set aside.
Add the sugars and unsalted butter to a stand mixer. Using the paddle attachment, beat until light and fluffy, about 2 minutes. Add the eggs one at a time, beating well after each addition.
Remove the bowl from the mixer. Add the banana mixture to the sugar mixture and fold in with a spatula until well combined.
Add the flour mixture to the banana mixture and fold in with spatula just until combined. Do not over mix. Fold in dark chocolate chunks and chopped walnuts, if desired.
Pour the batter into prepared pan. Bake 65 to 70 minutes, or until a toothpick inserted in the center comes out clean.
Set aside to cool on a rack for 15 minutes.
Remove bread from pan, and cool completely before slicing.