Chocolate Caramel Shortbread Bars i.e. Twix

I saw this homemade Chocolate Caramel Shortbread a month ago and vowed to make it after Spain and once I had people to share the bars with... After all I love Twix and the recipe looked pretty simple. Last Tuesday I decided Carielle's Friday birthday gathering would be the perfect opportunity.

It should have been easy. Shortbread is a cake walk with the mini-food processor. Melting chocolate, even in the microwave like I did, is a no brainer. And I've made caramel before with success. Unfortunately this recipe had me cursing the stove (the first time in 3 years my rooommate has ever heard this happen apparently).

For reasons I can't determine my caramel went very wrong; it was a bubbling mass topped with separated butter that greased my entire oven top while I frantically tried to get the whole thing to congeal into a usable state. In the end I poured off the butter and managed to salvage a tasty, though slightly overchewy, mass of caramel for the bars. Not ideal.

Luckily the bars still tasted decadent and delicious, especially if I let them come to room temperature for about 4 hours. When I revisit the recipe I plan to sub a different caramel recipe for layer 2 - a normal one that uses a candy thermometer. These bars are worth a try but be cautious. If you figure out how to NOT screw up the caramel please let me know and, oh, don't cut the bars until they are room temperature or the chocolate will crack.

Chocolate Caramel Shortbread (from the same blog but not the one she made)
Makes 12

½ cup butter, plus extra for greasing
Generous 1 cup all purpose flour
Generous ¼ cup superfine sugar

Filling and topping
¾ cup butter
Generous ½ cup superfine sugar
3 tbsp dark corn syrup
14 oz/400 g canned sweetened condensed milk
7 oz/200 g semisweet chocolate, broken into pieces

Preheat the oven to 350°F/180°C. Grease a 9-inch/23-cm square, shallow cake pan and line the bottom with parchment paper.

Place the butter, flour, and sugar in a food processor and process until it starts to bind together. Press into the prepared pan and level the top. Bake in the preheated oven for 20-25 minutes, or until golden.

Meanwhile, make the filling. Place the butter, sugar, corn syrup, and condensed milk in a heavy-bottom saucepan. Heat gently until the sugar has dissolved. Bring to a boil, then reduce the heat and let simmer for 6-8 minutes, stirring until very thick. Pour over the shortbread and let chill in the refrigerator for 2 hours, or until firm.

Place the chocolate in a heatproof bowl. Set over a saucepan of gently simmering water and stir until melted. Let cool slightly, then spread over the caramel. Let chill In the refrigerator for 2 hours, or until set. Cut the shortbread into 12 pieces and serve.