Buttery shortbread, creamy peanut butter filling and chocolate on top make these peanut butter shortbread bars impossible to resist. They’re essentially a peanut butter cup with a shortbread cookie base. 
These bars are similar to millionaire’s shortbread — or a caramel slice — except the middle layer is a sweet, creamy peanut butter filling rather than caramel. A tender, buttery shortbread forms the base and milk chocolate tops the bars. The middle layer is the star: smooth, sweetened peanut butter that tastes like the filling of a peanut butter cup.
The recipe is straightforward, though it involves three layers, so there are a few steps. Even a beginner baker can make these successfully.
3-Layer Peanut Butter Shortbread Bars
The shortbread base is made with simple ingredients: butter, sugar, flour, cornstarch and a pinch of salt. Cornstarch helps keep the shortbread tender; if you don’t have it, you can substitute an extra tablespoon of flour. The base is not overly sweet — buttery, tender and slightly crisp. Press the dough into a lined 8×8 inch (20×20 cm) pan and bake for about 22–25 minutes. 
Once the shortbread is baked and cooled, prepare the peanut butter layer. It’s similar to the filling in no-bake peanut butter bars and has the familiar peanut butter cup flavor. Combine softened butter, smooth peanut butter, vanilla and powdered sugar to form a thick, spreadable filling. Press the mixture evenly over the cooled shortbread base, then chill while you melt the chocolate topping. 
The chocolate topping is simply melted chocolate with a touch of butter so it slices cleanly. The recipe uses 4 oz milk chocolate and 2 oz dark chocolate, but use whatever you prefer: milk, dark or semi-sweet all work well. When melting chocolate, use medium power in the microwave and stir frequently to avoid overheating, which can make chocolate grainy or lumpy. Pour the melted chocolate over the peanut butter layer and chill until set. 
Pro Tip: When the chocolate is about 75% set, lightly score the top with a thin, sharp knife in the places where you plan to cut. Scoring while the chocolate is still a little soft helps you get clean slices without cracking the chocolate once it’s fully hardened.
These bars are rich but not cloyingly sweet — they deliver that classic peanut butter cup flavor on a buttery shortbread base. They’re easy to make and perfect for peanut butter lovers.
If you enjoy peanut butter cups, try these related desserts (recipe names kept as reference):
- Peanut butter pie
- Peanut butter cup cookies
- Chocolate peanut butter fudge (Buckeye fudge)
Peanut Butter Shortbread Bars
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Equipment
-
8×8 inch (20×20 cm) baking pan
Ingredients
Shortbread Base
- 2/3 cup unsalted butter, softened
- 1/3 cup caster sugar
- 1 1/3 cup all-purpose flour
- 1 tablespoon cornstarch
Peanut Butter Layer
- 3 tablespoons unsalted butter, softened
- 1 cup smooth peanut butter*
- 1 teaspoon vanilla extract
- 1 1/3 cup powdered sugar
Chocolate Topping
- 6 oz chocolate* (about 1 cup; typically 4 oz milk + 2 oz dark)
- 1 tablespoon unsalted butter
Instructions
Shortbread Base
- Preheat the oven to 325°F (160°C). Line an 8×8 inch (20×20 cm) pan with parchment paper, leaving an overhang for easy removal, or line with foil and lightly grease.
- In a medium bowl, beat the softened butter and sugar until combined.
- Gently mix in the flour and cornstarch until just combined.
- Press the mixture into the bottom of the prepared pan in an even layer.
- Bake for 22–25 minutes, until the top is set and the edges are just beginning to brown. Remove from the oven and cool fully in the pan (about 1 hour).
Peanut Butter Layer
- In a medium bowl, beat the butter and smooth peanut butter together until combined.
- Add vanilla and powdered sugar, then beat on low until the mixture is thick and slightly dry in texture.
- Press the peanut butter mixture evenly over the cooled shortbread and smooth the top. Chill while preparing the chocolate.
Chocolate Topping
- Chop the chocolate finely and place it in a heatproof bowl with the butter cut into small pieces.
- Microwave on medium power for 45 seconds, stir, and continue in short bursts, stirring between each, until smooth. Avoid high power to prevent graininess.
- Pour the chocolate over the peanut butter layer and smooth the surface. Return the pan to the fridge to set.
Slicing & Serving
- When the chocolate is about 75% set (still slightly glossy but not wet), lightly score the top where you plan to cut. This helps achieve clean slices.
- Once fully set, lift the bars from the pan using the parchment overhang and place on a cutting board. Slice with a sharp knife and serve.
Notes
- Use smooth, stabilized peanut butter (brand-name spreads like Skippy, Jif or Kraft). Avoid natural or oil-separated peanut butter.
- Any chocolate works: milk, dark or semi-sweet. Six ounces of chocolate equals about 1 cup of chocolate chips. Chopped chocolate melts more evenly than chips, but chips are fine.
- You can double the recipe in a 9×13 inch pan. Bars will be slightly thicker and the shortbread may need 25–30 minutes to bake.
- Store in an airtight container at room temperature up to 4 days, or refrigerated up to 1 week. Refrigerate if your kitchen is warm.
- Nutrition information is an estimate per slice assuming the pan is cut into 9 equal pieces.
Nutrition
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