Instructions:
- Preheat oven to 350°F (175°C). Grease and flour a standard 9x5 inch loaf pan, or line it with parchment paper, leaving an overhang.
- Whisk together the flour, baking soda, salt, and cinnamon in a medium bowl. Set aside.
- In a large bowl, beat the softened butter with both sugars until light and fluffy (about 2-3 minutes). Beat in the eggs one at a time, then stir in the mashed bananas and vanilla extract until just combined.
- Gradually add the dry mixture to the wet mixture. Mix just until barely combined; do not overmix. Stir in the milk until incorporated.
- Prepare the swirl mixture: Microwave the peanut butter and chocolate chips together in 30-second bursts until smooth and melted. Stir in the hot water or coffee to loosen slightly.
- Transfer half of the banana bread batter to the prepared loaf pan. Dot the top evenly with half of the peanut butter chocolate mixture. Top with the remaining batter, then dollop the rest of the swirl mixture over the top.
- Using a butter knife or small skewer, gently cut through the batter 3-4 times in an 'S' pattern to create the swirl effect. Do not over-swirl.
- Bake for 55 to 65 minutes, or until a wooden skewer inserted into the centre comes out with just a few moist crumbs attached.
- Let the bread cool in the pan for 15 minutes before carefully lifting it out onto a wire rack to cool completely before slicing.