Ingredients:

Instructions:

  1. Preheat oven to 350°F (175°C). Grease and flour a 9x5 inch loaf pan, or line it with parchment paper leaving an overhang.
  2. In a medium bowl, whisk together the flour, baking soda, cinnamon, and salt. Set aside.
  3. In a large bowl, cream the softened butter and granulated sugar together until light and fluffy (about 2–3 minutes).
  4. Beat in the eggs one at a time. Stir in the mashed bananas and vanilla extract until just combined.
  5. Gently fold the dry ingredients into the wet ingredients in two additions, mixing only until just combined. Do not overmix! Gently fold in the sour cream or yogurt until no streaks remain.
  6. Prepare the swirl: In a small bowl, whisk together the peanut butter, powdered sugar, and milk/cream until smooth and spreadable.
  7. Spoon half of the banana batter into the prepared loaf pan. Dollop the peanut butter mixture randomly over the top. Cover with the remaining banana batter.
  8. Use a butter knife to gently run through the batter in an 'S' pattern 2-3 times to create a marbleized swirl. Be careful not to over-swirl.
  9. Bake for 55–65 minutes, or until a skewer inserted into the center comes out with moist crumbs attached.
  10. Let the loaf cool in the pan for 15 minutes before carefully turning it out onto a wire rack to cool completely before slicing.