Preheat your oven to 350°F (175°C) to ensure even baking.
Grease your loaf pan with butter or non-stick spray, or line it with parchment paper.
In a large mixing bowl, cream together the room temperature butter, brown sugar, and granulated sugar until fluffy. Add the creamy peanut butter and mix until well combined. Beat in the eggs one at a time, then stir in the smashed bananas.
In another bowl, whisk together the all-purpose flour and baking soda.
Gradually add the dry ingredients to the wet mixture, folding everything together with a rubber spatula.
Fold in 1.5 cups of chopped Reeses Peanut Butter Cups, reserving the remaining 0.5 cup for topping.
Pour the batter into the prepared loaf pan and sprinkle the remaining Reeses Peanut Butter Cups on top.
Bake in the preheated oven for 55-65 minutes, or until a toothpick comes out clean.
Let the bread cool in the pan for about 10 minutes, then transfer it to a cooling rack to cool completely before slicing.
