Preheat your oven to 350°F (175°C). Grease your loaf pan with butter or line it with parchment paper for easy removal.
In a mixing bowl, whisk together the all-purpose flour, baking soda, and salt until well combined. Set aside.
In a separate large bowl, beat the softened butter, light brown sugar, and granulated sugar together until light and fluffy, about 2-3 minutes.
Add the eggs, mashed bananas, sour cream, and vanilla extract to the butter mixture. Mix until well incorporated.
Gradually add the dry ingredients to the wet mixture, stirring just until combined. Be careful not to overmix; a few lumps are fine.
Gently fold in the mini peanut butter cups until evenly distributed throughout the batter.
If desired, mix in the whipped peanut butter for an extra creamy texture. Optionally sprinkle granulated sugar over the top.
Pour the batter into your prepared loaf pan, smoothing the top with a spatula. Bake for 55-65 minutes, or until a toothpick inserted comes out clean.
Once baked, remove the banana bread from the oven and allow to cool in the pan for about 10 minutes. Then transfer to a wire rack to cool completely before slicing.
