Reese’s Millionaire Shortbread

Last week I grabbed a millionaire shortbread from a bakery and halfway through the first bite I thought: this needs peanut butter. Layers of buttery shortbread, thick peanut butter caramel, and a glossy chocolate ganache topped with actual Reese’s cups. It’s basically a homemade candy bar you cut into squares.

The peanut butter caramel is where this recipe earns its name. You’re stirring condensed milk, brown sugar, butter, and peanut butter on the stove for 10-15 minutes until it thickens and is deeply golden and spreadable. It tastes like the filling of a really good peanut butter cup, but richer. The ganache on top stays soft enough to slice through cleanly without cracking, and pressing the Reese’s cups into it while it’s still tacky means they actually stick instead of sliding off when you cut into bars.

this recipe

I made these for a weekend get-together and they disappeared faster than anything else on the table. If you’re a Reese’s person, this is the layered dessert bar version of that. Cut them small because they’re really rich.

Why you’ll love this recipe

Peanut butter caramel – stirring peanut butter into homemade caramel gives you a layer that’s thicker and nuttier than plain caramel, with a texture that holds its shape when you bite through but still feels gooey.

Actual Reese’s cups on top – pressing halved or quartered peanut butter cups into the ganache before it sets means every square gets a visible, recognizable hit of that chocolate-peanut butter combo people already love.

Three textures in one bite – the shortbread base is crumbly and buttery, the caramel is chewy and thick, and the ganache is smooth and glossy, so each layer stays distinct instead of blending together.

Ingredients

• Unsalted butter
• Granulated white sugar
• Egg yolk
• Vanilla extract
• All-purpose flour
• Sweetened condensed milk
• Light brown sugar
• All-natural peanut butter
• Heavy cream
• Semi-sweet chocolate chips
• Reese’s peanut butter cups

Equipment

• 9×9 inch square baking pan
• Parchment paper
• Hand mixer or stand mixer
• Medium saucepan
• Offset spatula

Tips for making Reese’s Peanut Butter Millionaire Bars

• Stir the caramel constantly – walking away from the saucepan even for a minute risks burning the bottom. The condensed milk and sugar mixture needs continuous motion to thicken evenly and develop that deep caramel colour without scorching. Your arm will get tired around the 10-minute mark, but keep going until it’s noticeably thicker and pulls away slightly from the sides of the pan.
• Use all-natural peanut butter – the kind where the oil separates on top gives you better control over sweetness since it doesn’t have added sugar. Regular peanut butter works too, but the caramel will end up sweeter and slightly looser in texture. If you use natural, give it a good stir before measuring so the oil incorporates.
• Chill the caramel layer completely – before pouring the ganache on top, the peanut butter caramel needs at least 30 minutes in the fridge to firm up. If it’s still warm or soft, the ganache will sink into it and you’ll lose the clean layered look when you slice into bars.
• Warm your knife for clean cuts – dip a sharp knife in hot water, wipe it dry, then slice. The heat softens the chocolate ganache just enough to cut through without cracking or shattering. Repeat between each cut for the cleanest edges.
• Press the Reese’s cups in while the ganache is tacky – if the ganache has already set hard, the peanut butter cups won’t stick and they’ll pop off when you try to cut the bars. Gently press them in within 5-10 minutes of spreading the ganache so they anchor in place.

Frequently Asked Questions

Can I substitute the peanut butter with another nut butter? Yes, almond butter or cashew butter will work and give you a slightly different flavour. Sunflower seed butter is a good nut-free option, though it can turn the caramel slightly greenish because of a natural chemical reaction with baking soda in some recipes (it’s harmless, just visual). Just make sure whatever you use is unsweetened so the caramel doesn’t end up too sugary.

How should I store these bars and how long do they last? Store them in an airtight container in the fridge for up to a week. The shortbread stays crisp, the caramel holds its shape better when chilled, and the ganache won’t soften too much. Let them sit at room temperature for 5-10 minutes before serving if you want the caramel layer slightly softer. They don’t freeze well because the ganache can separate when thawed.

Can I make these ahead of time for a party or bake sale? Absolutely. These actually benefit from sitting in the fridge overnight because the layers firm up and slice even cleaner. Make them up to two days ahead, keep them covered, and cut them the day you’re serving. If you’re transporting them, leave them whole and slice on-site so the chocolate doesn’t crack from jostling around.

Why did my caramel turn out too soft or runny? You probably didn’t cook it long enough. The caramel needs a full 10-15 minutes of constant stirring over low heat after it starts to boil. It should thicken to the consistency of thick honey or corn syrup and coat the back of a spoon. If it’s still thin and pourable like condensed milk, it needs more time. Also make sure you’re using a true simmer, not high heat, or it can seize up instead of thickening smoothly.

Make sure to tag me @theflournook on social media and leave a review below if you make this Reese’s peanut butter millionaire bar! To pin this recipe and save it for later, you can use the button on the recipe card, the buttons above or below this post, or on any of the photos above.

Happy baking!

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