Preheat oven to 350°F. Grease or spray a 9x5-inch loaf pan with nonstick spray. Set aside.
Using a hand or stand mixer, cream the butter and both sugars together until well combined and fluffy.
½ cup salted butter, ½ cup granulated sugar, ½ cup brown sugar
Beat in the eggs and sliced bananas. Set aside.
2 large eggs, 3 ripe bananas
In a separate large mixing bowl, use a spatula or wooden spoon to mix together 1½ cups flour, baking soda, baking powder, salt, and mini chocolate chips. Set this bowl aside as well.
2 cups all-purpose flour, 1 teaspoon baking soda, ½ teaspoon baking powder, ½ teaspoon kosher salt, ½ cup mini chocolate chips
In another separate bowl, stir together the blueberries and the remaining ½ cup of flour to coat the blueberries lightly.
2 cups blueberries
Pour the banana batter into the dry flour mixture. Stir just until moistened. Make sure to scrape the sides and bowl of the bowl to incorporate all the ingredients well.
Very gently fold the blueberries into the batter. Do not overmix or the blueberries will bleed their color into the mixture.
Scrape the batter into the loaf pan and spread evenly. (For a nicer finish, add just a few chocolate chips and blueberries to the top of the uncooked loaf and press them in gently)
Bake for 50 minutes. Insert a cake tester, toothpick, or thin-bladed knife. If the batter is not set (the cake tester comes out wet), continue baking for another 5-10 minutes. If the loaf begins to brown too quickly, tent with foil.
Place the pan on a cooling rack and let sit for 10 minutes. Turn the loaf pan over and slide the banana bread out of the pan. Allow it to cool on the cooling rack.