Preheat the oven to 330°F (165°C) or 300°F (150°C) if using a fan-assisted oven. Lightly grease a 9x5-inch (23x12-cm) loaf pan with cooking spray or butter and line with parchment paper all the way up the sides for easier handling later.
In a medium-sized bowl, sift and combine together the flour, baking soda and salt. Set aside.
In a separate mixing bowl, combine together the peanut butter, sunflower oil, granulated sugar and dark brown sugar using an electric hand mixer. Beat until it's smooth and combined.
Next, add in the mashed banana, eggs, sour cream and vanilla extract. Beat until evenly combined.
Switch to a wooden spoon or a silicone spatula and fold in the dry ingredients.
Lastly, add in the mini chocolate chips and stir until evenly distributed. Pour the batter into the prepared pan and sprinkle the top with extra mini chocolate chips.
Bake in a preheated oven for 55-60 minutes or until the skewer inserted in the middle comes out mostly clean; with a few moist crumbs. Don't overbake it.
Once it's done, take the pan out of the oven and place on a wire rack to cool completely before removing the banana bread from the pan.
Store the banana bread in an airtight container, either at room temperature or fridge if you like your banana bread cold.
Serve with a cup of coffee, milk or tea and enjoy!