Easy Millionaire Shortbread Recipe - Chocolate Caramel Slice

If a Twix bar grew up, got a sophisticated degree, and moved into a fancy bakery, it would undoubtedly be this millionaire shortbread. These thick, gooey chocolate caramel slice bars are the ultimate indulgence, featuring three irresistible layers: a rich, buttery shortbread base, a soft and chewy caramel condensed milk center, and a smooth, decadent chocolate topping. Get ready to master this classic treat with our fail-proof caramel cues, US-friendly measurements, and a step-by-step approach that guarantees success.
This recipe is perfect for bake sales, holiday gatherings, or simply elevating your coffee break. Our millionaire shortbread bars are sturdy enough to pack and share, yet they melt in your mouth with every bite. We use simple grocery store ingredients, and while a candy thermometer is recommended for perfect caramel, it's not strictly required thanks to our clear visual cues.

Ingredients

• This recipe is designed for a 9x9-inch (23x23 cm) metal baking pan.
• For the Shortbread Base:
• 1 cup (2 sticks / 226g) unsalted butter, softened
• ½ cup (100g) granulated sugar
• 2 cups (240g) all-purpose flour
• ¼ teaspoon fine sea salt
• 1 teaspoon vanilla extract (optional, but adds depth)
• For the Caramel Layer:
• 1 (14-ounce / 397g) can sweetened condensed milk (do NOT swap for evaporated milk)
• ½ cup (1 stick / 113g) unsalted butter, cut into pieces
• ½ cup (100g) light brown sugar, packed
• 2 tablespoons light corn syrup or golden syrup (see notes for substitutions)
• ½ teaspoon fine sea salt
• 1 teaspoon vanilla extract
• For the Chocolate Topping:
• 1 ½ cups (255g) semi-sweet or dark chocolate chips, or chopped bar
• 2 tablespoons heavy cream
• Flaky sea salt, for sprinkling (optional, but highly recommended)

Directions

1. Before You Begin: Pan PrepLine your 9x9-inch metal pan with parchment paper or foil, leaving an overhang on all sides to create a "sling." Lightly grease the exposed sides of the pan for extra easy release.
2. Make the Shortbread Base
   1. In a large bowl with an electric mixer (or by hand), beat the softened butter and granulated sugar together on medium speed until the mixture is light, fluffy, and pale in color (about 2-3 minutes).
   2. Beat in the vanilla extract (if using).
   3. Gradually add the all-purpose flour and salt, mixing on low speed just until a crumbly dough forms and no dry streaks of flour remain. Be careful not to overmix.
   4. Scatter the shortbread dough evenly into your prepared pan. Use the back of a spoon or your fingers (you can place a piece of parchment over the dough to prevent sticking) to press the dough firmly and evenly into the bottom of the pan.
   5. Lightly dock the shortbread all over with a fork. This helps prevent it from puffing up unevenly.
   6. Bake in a preheated oven at 350°F (175°C) for 20-25 minutes, or until the edges are just turning a light golden brown. The center might still look pale.
   7. Remove from the oven and let the shortbread cool completely in the pan while you prepare the caramel.
3. Cook the Caramel
   1. In a heavy-bottomed saucepan (this is crucial to prevent scorching!), combine the sweetened condensed milk, butter pieces, light brown sugar, and light corn syrup (or golden syrup).
   2. Place the saucepan over medium-low heat. Stir constantly with a wooden spoon or heat-safe spatula until the butter is completely melted and the sugar is fully dissolved. You shouldn't feel any sugar grains when rubbing a bit of the mixture between your fingers. This low-and-slow start is key to preventing a grainy caramel.
   3. Once dissolved, increase the heat slightly to medium. Continue to stir constantly, scraping the bottom and corners of the pan to prevent sticking and burning. The mixture will begin to bubble steadily and thicken.
   4. Cook the caramel for 8-12 minutes, or until it reaches a target temperature of 220–225°F (104–107°C) on a candy thermometer. If you don't have a thermometer, look for a visual cue: the caramel should be a rich peanut butter-like color, thick, glossy, and pull away from the sides of the pan slightly when stirred.
   5. Immediately remove the pot from the heat. Stir in the vanilla extract and salt.
   6. Pour the hot caramel evenly over the cooled shortbread base in the pan. Use an offset spatula to smooth the top.
   7. Let the caramel cool in the pan until it's set enough to support the chocolate layer without melting into it. This can take 1-2 hours at room temperature, or about 30-45 minutes in the refrigerator.
4. Add the Chocolate Layer
   1. In a microwave-safe bowl, combine the chocolate chips (or chopped chocolate) and heavy cream.
   2. Heat in the microwave in 30-second bursts, stirring well after each burst, until the chocolate is completely melted and the mixture is smooth and glossy. Alternatively, you can melt it over a double boiler.
   3. Let the ganache cool briefly for about 5-10 minutes. This prevents it from being too hot and melting the caramel layer underneath.
   4. Pour the slightly cooled ganache over the set caramel layer, spreading it evenly with an offset spatula.
   5. Gently tap the pan a few times on the counter to level the chocolate and release any air bubbles.
   6. If using, sprinkle flaky sea salt over the chocolate layer immediately.
5. Cool, Slice & Serve
   1. Cool the millionaire's shortbread completely. This can be done at room temperature for a softer chocolate topping (takes 2-3 hours) or in the refrigerator for faster setting and firmer chocolate (about 1 hour). Ensure it's fully set before slicing.
   2. Once completely cool and firm, use the parchment paper overhang to lift the entire slab of millionaire shortbread out of the pan and onto a clean cutting board.
   3. For neat, clean squares: warm a large, sharp knife under hot running water, then wipe it completely dry. Cut straight down through the bars. Wipe the knife clean and re-warm it between each cut to ensure smooth edges and prevent the chocolate from cracking.
   4. Cut into your desired size – typically 16 large squares or 25-36 smaller, bite-sized pieces.