adapted from Nigella Lawson | makes 16-24 bars
1 1/2 cups all-purpose flour
1/4 cup sugar
1 ½ cups (3 sticks) unsalted butter; divided use
1 (14-ounce) can sweetened condensed milk
4 tablespoons light corn syrup
12 ounces semisweet chocolate
1 teaspoon vanilla fleur de sel (sea salt)
1. Preheat the oven to 325 degrees.
2. Put the flour and sugar into a bowl and rub in 12 tablespoons of the butter (note: I used my food processor for this step), clumping the dough together to form a ball.
3. Press this sandy shortbread mixture into a 9-inch square pan that has been greased and the bottom lined with parchment paper; smooth it with either your hands or a spatula. Pierce it with a fork and cook for 5 minutes, then lower the oven to 300 degrees, and cook for a further 30-40 minutes until it is pale golden and no longer doughy. Let it cool in the pan.
4. In a deep microwave safe bowl, Melt the remaining butter (12 tablespoons) for 2-3 minutes, then add the condensed milk and syrup. Whisk the mixture well until the butter is thoroughly incorporated.
5. Heat in the microwave for 6-7 minutes until it is boiling, stirring thoroughly every 30 seconds. Be careful to stir often and DO NOT leave unattended because this will boil over and create a mess! It’s ready when it’s thickened and turned a light golden brown. Pour this molten toffee evenly over the cooled shortbread and leave it to set.
5. Break the chocolate into pieces and melt it in a bowl in the microwave. Pour and spread it over the caramel mixture (the less you touch it, the shinier it will be).
6. If you are incorporating the fleur de sel, sprinkle it over the chocolate and allow the bars to cool.
7. Once set, cut the caramel shortbread into pieces. The squares can be stored in the fridge to keep them firm, though if it’s winter that shouldn’t be necessary.