Millionaire's Shortbread

Name: Millionaire's Shortbread
Prep time: 36 min
Cook time: 38 min
Total time: 1 h 14 min
Yield: 16 servings
Cuisine: British
Ingredients: 1½ cups (190 g) all-purpose flour, spooned into the cup and leveled; ¼ cup (30 g) cornstarch; ⅓ cup (65 g) granulated sugar; ¼ tsp (1½ g) fine salt; ¾ cup (1½ sticks) (170 g) unsalted butter, cool but pliable (about 65°F / 18°C), cut into ½-inch cubes; ½ cup (1 stick) (113 g) unsalted butter, cut into tablespoon-size pieces; ½ cup (100 g) light brown sugar, packed; 2 tbsp (42 g) golden syrup or light corn syrup; 14 oz can (397 g) sweetened condensed milk, shaken, full can; ¼ tsp (1½ g) fine salt; 1 tsp (5 ml) pure vanilla extract; 7 oz (200 g) semisweet or dark chocolate (55–70% cacao), finely chopped; 1 tsp (5 ml) neutral oil (such as vegetable or canola); flaky sea salt, for sprinkling, to taste (optional)

From the MyKitchenBank Kitchen

A buttery, crumbly shortbread base topped with a thick, chewy brown sugar caramel and a snappy layer of dark chocolate. This classic British tray bake cuts into neat squares and keeps well, so it's ideal for making ahead.

Prep: 36 min
Cook: 38 min
Wait: 2 hr 5 min
Total: 3 hr 19 min
Makes: 16 bars (2-inch / 5 cm squares) from a 9-inch pan

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Ingredients

16 servings

For the shortbread
1½ cups (190 g) all-purpose flour, spooned into the cup and leveled
¼ cup (30 g) cornstarch
⅓ cup (65 g) granulated sugar
¼ tsp (1.5 g) fine salt
¾ cup (1½ sticks) (170 g) unsalted butter, cool but pliable (about 65°F / 18°C), cut into ½-inch cubes
For the caramel
½ cup (1 stick) (113 g) unsalted butter, cut into tablespoon-size pieces
½ cup (100 g) light brown sugar, packed
2 tbsp (42 g) golden syrup or light corn syrup
14 oz can (397 g) sweetened condensed milk, shaken, full can
¼ tsp (1.5 g) fine salt
1 tsp (5 ml) pure vanilla extract
For the topping
7 oz (200 g) semisweet or dark chocolate (55–70% cacao), finely chopped
1 tsp (5 ml) neutral oil (such as vegetable or canola)
flaky sea salt, for sprinkling, to taste (optional)

Equipment (9)

9×9-inch (23×23 cm) square baking pan
Parchment paper
Medium heavy-bottomed saucepan (3-quart / 3 L)
Heatproof spatula or wooden spoon
Candy thermometer (optional but recommended)
Large mixing bowl
Fork for docking
Microwave-safe bowl or small saucepan and heatproof bowl for melting chocolate
Long, sharp knife and a jug of hot water

Steps

Before you start

Take the butter for the shortbread out of the fridge about 30 minutes ahead so it is cool but pliable (it should dent when pressed, not be greasy).
Read the timing: the bars need about 2 hours of cooling and chilling between layers, so plan for a 3+ hour project.
Line the pan before you start, and keep a candy thermometer handy for the caramel (it is optional but the most reliable guide).
Have everything for the caramel measured and ready; once it is on the heat you can't leave it.

1
Line the panOven 350°F / 175°C
- Position a rack in the center of the oven and heat to 350°F (175°C).
- Line a 9×9-inch (23 cm) square pan with a single sheet of parchment, leaving 2 inches (5 cm) overhanging on two opposite sides to use as handles later.
- Press the paper into the corners.
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Ready when: Parchment lies flat against the pan with handles on two sides.
Tip: A small dab of butter under the paper corners helps it stay in place.
2
Make shortbread dough
- In a large bowl whisk the flour, cornstarch, granulated sugar and salt_base together.
- Add the cool butter cubes and rub them into the dry ingredients with your fingertips (or mix with a fork) for about 3 minutes, until the mixture looks like damp sand and clumps when squeezed.
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Ready when: No dry flour remains, and a handful squeezed in your fist holds together.
Tip: Don't knead or overwork it; warm, overworked dough bakes up greasy and tough.
3
Press and dock
- Tip the crumbs into the lined pan and press firmly and evenly across the bottom and into the corners, using the flat bottom of a measuring cup to smooth the surface.
- Prick all over at 1-inch (2.5 cm) intervals with a fork.
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Ready when: The base is a smooth, even layer about ½ inch (1 cm) thick.
Tip: Press firmly; a loosely packed base crumbles when cut.
4
Bake the baseOven 350°F / 175°C
- Bake at 350°F (175°C) for 26 to 30 minutes, rotating the pan once halfway, until the surface is pale golden and the edges are a deeper golden brown.
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Ready when: Edges are golden brown and the center looks dry and set, not shiny or raw.
Tip: Don't wait for the center to brown deeply or the base will turn hard and dry.
5
Cool the base
- Set the pan on a wire rack and cool for 20 minutes while you make the caramel.
- The base should be warm or room temperature, not hot, when you add the caramel.
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Ready when: The pan is only just warm to the touch.
6
Cook the caramel
- In a 3-quart (3 L) heavy saucepan combine butter_caramel, brown sugar, golden syrup, condensed milk and salt_caramel.
- Set over medium-low heat and stir constantly with a spatula, scraping the corners, until the butter melts and the sugar dissolves, about 3 minutes.
- Raise to medium and bring to a gentle bubble, then cook, stirring constantly, for 6 to 8 minutes more, until thick and deep golden like peanut butter.
- Remove from the heat and stir in the vanilla.
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Ready when: Caramel reads 230°F (110°C) on a candy thermometer, or the spatula leaves a trail on the pan bottom that closes slowly; it is thick and pulls away from the sides.
Tip: Never stop stirring; condensed milk scorches quickly on the bottom. If it splits and looks oily, whisk in 1 tablespoon of hot water off the heat.
7
Pour the caramel
- Immediately pour the hot caramel over the slightly cooled shortbread and tilt the pan or use an offset spatula to spread it to the edges and corners.
- Work quickly because it thickens as it cools.
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Ready when: Caramel forms a smooth, even layer that reaches all four corners.
Tip: A spatula dipped in hot water spreads sticky caramel more easily.
8
Set the caramel
- Leave the pan on the counter for 15 minutes, then refrigerate it for 30 minutes, until the caramel is firm and no longer sticks to a lightly touched fingertip.
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Ready when: The surface is matte and firm when lightly pressed.
Tip: Chocolate poured on warm caramel swirls into it and makes cutting messy.
9
Melt the chocolate
- Put the chopped chocolate and oil in a microwave-safe bowl.
- Microwave in 30-second bursts at 50% power, stirring after each, for 1½ to 2 minutes total, until about three-quarters melted.
- Stir until completely smooth and glossy.
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Ready when: Chocolate is completely smooth, fluid and only warm, not hot.
Tip: Overheated chocolate turns grainy and thick; stop heating while a few small pieces remain and stir them in.
10
Top with chocolate
- Pour the chocolate over the set caramel and spread it gently to the edges with an offset spatula.
- Sprinkle with flaky salt, if using.
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Ready when: The chocolate completely covers the caramel in an even, glossy layer.
11
Chill until firm
- Refrigerate for at least 1 hour, until the chocolate is completely hard.
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Ready when: Chocolate is hard and doesn't dent when pressed.
12
Cut into bars
- Let the pan sit at room temperature for 10 minutes.
- Lift the slab out using the parchment handles and set it on a cutting board.
- Dip a long, sharp knife in hot water, wipe it dry, and cut into 4 strips, then each strip into 4 squares.
- Press straight down rather than sawing, and re-heat and wipe the knife between cuts.
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Ready when: Each bar has clean, sharp layers with a crisp chocolate top.
Tip: Cutting straight from the fridge cracks the chocolate; the short rest lets it soften slightly.

Good to know

Tips

Use a heavy-bottomed saucepan and constant stirring to prevent the caramel scorching.
A thermometer reading of 230°F (110°C) gives a caramel that is chewy but cuts cleanly; cooking much hotter makes it hard to bite.
Wipe the knife clean and hot between every cut for neat, smear-free layers.
Use parchment overhang to lift the slab out of the pan before cutting, as cutting in the pan scratches it and makes removal tricky.

Make ahead

"Bake the shortbread base up to 1 day ahead and keep it covered in the pan at room temperature. The finished bars can be made up to 3 days ahead and kept chilled."

Storage & reheating

"Room temperature: up to 1 day in a cool kitchen (under 68°F / 20°C) in an airtight container. Fridge: up to 5 days in an airtight container with parchment between layers; let bars stand 15 minutes before serving. Freezer: up to 2 months, wrapped well in layers; thaw overnight in the fridge. No reheating needed."

Substitutions

golden syrup or light corn syrup → light corn syrup or honey. Corn syrup gives the same texture; honey adds a slight floral flavor.
semisweet or dark chocolate (55–70% cacao) → milk chocolate. Sweeter and softer-setting; the bars will be a little harder to cut cleanly, so chill them well.
unsalted butter → salted butter. Use salted butter and omit the salt_base.
cornstarch → more all-purpose flour (30 g / ¼ cup). The base will be slightly less tender but still works.