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Stack of 3 peanut butter shortbread bars with a glass of milk.
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Peanut Butter Shortbread Bars

Buttery shortbread, creamy peanut butter filling and chocolate on top make these peanut butter shortbread bars impossible to resist. They're like a peanut butter cup with a layer of cookie on the bottom. Like a millionaire's shortbread - but with peanut butter instead of caramel
Course Dessert
Cuisine American
Keyword Peanut Butter Millionaire's Shortbread, Peanut Butter Shortbread Bars
Prep Time 30 minutes
Cook Time 22 minutes
Cooling and Chilling 2 hours
Total Time 3 hours
Servings 9 slices
Calories 595kcal

Equipment

  • 8x8 inch (20x20 cm) baking pan

Ingredients

Shortbread Base

  • cup unsalted butter softened
  • cup caster sugar aka white sugar
  • 1 ⅓ cup all-purpose flour aka plain flour
  • 1 tablespoon cornstarch

Peanut Butter Layer

  • 3 tablespoons unsalted butter softened
  • 1 cup smooth peanut butter*
  • 1 teaspoon vanilla extract
  • 1 ⅓ cup powdered sugar

Chocolate Topping

  • 6 oz chocolate* I typically use 4 oz milk chocolate and 2 oz dark chocolate
  • 1 tablespoon unsalted butter

Instructions

Shortbread Base

  • Preheat the oven to 325F degrees and line an 8x8 inch (20x20 cm) pan with parchment paper, leaving an overhang around the edges. Or line with aluminum foil and lightly grease.
  • In a medium bowl, beat together the butter and sugar until combined.
  • Carefully mix in the flour and cornstarch, only mixing until just combined.
  • Press the mixture into the bottom of the lined pan to form an even layer.
  • Bake in the preheated oven for 22-25 minutes or until the top looks completely set. The edges may just be starting to brown.
  • Remove from the oven (keeping the bars in the pan) and cool fully (usually at least 1 hour).

Peanut Butter Layer

  • In a medium bowl, beat together the butter and peanut butter.
  • Add in the vanilla extract and powdered sugar. Beat the mixture together starting with the mixer on low speed. It should be thick and almost a little dry feeling when you're done.
  • Press the peanut butter mixture on top of the cooled shortbread base and spread the top flat.
  • Pop the bars in the fridge as you make the chocolate topping.

Chocolate Topping

  • Chop the chocolate into very small pieces and place in a heatproof bowl with the butter chopped into a few small pieces.
  • Microwave on medium power (do not microwave on high or standard power, or the chocolate can get grainy). for 45 seconds. Remove from the microwave and stir. Repeat the process until the chocolate is smooth.
  • Pour the chocolate on top of the peanut butter layer and smooth the top.
  • Return the bars to the fridge for the chocolate to harden.

Slicing & Serving

  • When the chocolate on top is about 75% hardened (it will look slightly glossy, but no longer wet) gently score the top of the bars with a thin, sharp knife (such as a paring knife) where you plan to slice the bars. Return to the fridge to continue hardening.
  • Once the chocolate is set, lift the bars out of the pan using the overhang of the parchment paper and place on a cutting board. Slice the bars with a sharp knife (not a table knife), and serve.

Notes

  1. Make sure to use smooth, stabilized peanut butter. Do not use natural, whipped or homemade peanut butter because it can separate and leak oil. Peanut butter such as Skippy, Jiff or Kraft work perfectly.
  2. Feel free to use your favorite kind of chocolate - milk, dark or semi-sweet work perfectly. 6 oz of chocolate is equal to 1 cup of chocolate chips. I prefer to use chopped chocolate because it melts more easily than chocolate chips and is less likely to become grainy - but chocolate chips work too.
  3. This recipe can be doubled and made in a 9x13 inch pan. The bars will be a little thicker if using a 9x13 inch pan, and the bake time for the shortbread layer will be closer to 25-30 minutes. 
  4. Store bars in an airtight container at room temperature for up to 4 days, or in the fridge for up to 1 week. If your kitchen is particularly warm, you may want to store them in the fridge.
  5. Nutrition information is an estimate only and is based on 1 slice, assuming the pan is cut into 9 equal slices. 

Nutrition

Calories: 595kcal | Carbohydrates: 56g | Protein: 10g | Fat: 40g | Saturated Fat: 19g | Cholesterol: 50mg | Sodium: 138mg | Potassium: 265mg | Fiber: 3g | Sugar: 36g | Vitamin A: 576IU | Calcium: 25mg | Iron: 2mg