Preheat oven to 375°F. Line a standard 12-cup muffin pan with cupcake liners or lightly spray the wells with cooking spray. Set aside.
In a large mixing bowl, mash the bananas. Add in the brown sugar, granulated sugar, melted butter, sour cream, egg, and vanilla extract until smooth and well combined. Set aside.
3 ripe bananas, ½ cup brown sugar, ½ cup granulated sugar, ¼ cup unsalted butter, melted, ⅓ cup sour cream, 1 large egg, 1 teaspoon vanilla bean paste
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt by hand until well combined. Ensure there are no streaks of flour.
1¾ cups all-purpose flour, 1 teaspoon baking powder, ½ teaspoon baking soda, ¼ teaspoon kosher salt
Add the dry ingredients to the bowl of wet ingredients. Gently fold the flour mixture in using a spatula until just combined. Be careful not to overmix, as this can result in tough muffins.
Fold in the chocolate chunks with a rubber spatula until evenly distributed throughout the muffin batter.
1 cup semi-sweet chocolate chunks
Using a large cookie scoop or a spoon, divide the batter evenly among the muffin cups, filling each cup about ⅔rds full. Press a few extra chocolate chunks onto the tops of the muffins.
Bake for 18-20 minutes, or until the tops are golden brown and a toothpick inserted into the center of a muffin has a few moist crumbs clinging to it.
Remove the muffin tin from the oven and transfer it to a wire rack to cool for a few minutes. Once slightly cooled, remove the muffins from the tin and allow them to cool completely on a wire rack.
Serve these delicious banana chocolate chunk muffins warm or at room temperature.