Ingredients:

  • 1 cup (2 sticks) Unsalted Butter, softened
  • 1/2 cup Granulated Sugar
  • 1 cup Light Brown Sugar, packed
  • 1 cup Creamy Peanut Butter (for base)
  • 2 Large Eggs
  • 2 teaspoons Vanilla Extract (for base)
  • 2 1/4 cups All-Purpose Flour
  • 1 teaspoon Baking Soda
  • 1/2 teaspoon Kosher Salt
  • 1/2 cup (1 stick) Unsalted Butter, melted (for frosting)
  • 1/2 cup Creamy Peanut Butter (for frosting)
  • 3 cups Powdered Sugar (Icing Sugar), sifted
  • 3–5 tablespoons Whole Milk or Cream
  • 1 teaspoon Vanilla Extract (for frosting)

Instructions:

  1. Prep the Oven and Pan: Preheat oven to 350°F (175°C). Line a 9x13 pan with parchment paper, leaving an overhang on the two long sides to act as a sling. Lightly grease the exposed short ends.
  2. Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
  3. Cream Wet Ingredients: In the bowl of a stand mixer, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy (about 3–4 minutes). Scrape down the sides.
  4. Add Flavour and Structure: Beat in the 1 cup of peanut butter until well combined. Then, beat in the eggs one at a time, followed by the vanilla extract, ensuring each egg is fully incorporated before adding the next.
  5. Combine Wet and Dry: On low speed, gradually add the dry ingredients to the wet ingredients, mixing only until just combined. Do not overmix.
  6. Press and Bake: Press the dough evenly into the prepared 9x13 pan. Use slightly damp hands or a parchment-lined measuring cup to achieve a smooth, level surface.
  7. Bake: Bake for 25–30 minutes, or until the edges are golden brown and the centre is set. Remove from the oven and place on a wire rack to cool for 10 minutes while preparing the frosting.
  8. Melt the Butter: In a small saucepan or microwave-safe bowl, melt the 1/2 cup of butter completely.
  9. Combine Frosting Ingredients: In a large bowl, combine the melted butter, 1/2 cup peanut butter, vanilla, and 3 tablespoons of milk. Whisk thoroughly.
  10. Incorporate Sugar: Gradually beat in the sifted powdered sugar until a thick, spreadable frosting forms.
  11. Adjust Consistency: If the frosting is too stiff, add the remaining milk (1 tablespoon at a time) until it is smooth and easily spreadable.
  12. Frost: While the bars are still slightly warm (after the initial 10-minute rest), spread the frosting evenly over the top. The warmth helps the frosting adhere nicely to the cookie base.
  13. Cool Completely: Allow the bars to cool completely at room temperature (about 30–45 minutes) before lifting them out of the pan using the parchment paper sling. This is crucial for clean cuts.
  14. Cut and Serve: Cut the bars into 15 squares (5 rows by 3 rows) using a sharp knife.