Preheat your oven to 350°F. Line a 9x5-inch loaf pan with parchment paper, letting it overhang on the long sides. Spray exposed ends with non-stick spray.
In a medium bowl, mash the bananas with a fork until mostly smooth but with a few small lumps. Set aside.
In a large bowl, beat the butter and brown sugar together with a hand mixer on medium speed until light, fluffy, and pale, about 3 minutes.
Add the eggs one at a time, beating well after each, then beat in the vanilla extract.
In a separate bowl, whisk together the flour, baking soda, and salt.
With the mixer on low, add the flour mixture in three additions, alternating with the buttermilk in two additions, starting and ending with flour. Mix just until combined.
Switch to a rubber spatula. Gently fold in the mashed bananas and chocolate chips until evenly distributed.
Pour the batter into the prepared pan and smooth the top. Bake for 55-65 minutes, until a toothpick inserted in the center comes out with a few moist crumbs. Tent with foil if browning too quickly.
Let the bread cool in the pan on a wire rack for 15 minutes, then lift out using the parchment sling and cool completely on the rack.