Chocolate Caramel Shortbread

Have you ever had a serious kitchen disaster? Not just something you baked or cooked that didn’t turn out how you hoped, I mean a true catastrophe. I’ve heard of people accidentally using salt instead of sugar in a cake, or trying to brown something under a broiler and instead setting it on fire.

Until recently, I was pretty lucky. I had experienced plenty of minor mishaps, but nothing major. I had probably gotten a little cocky and lazy. This recipe put me back in my place!

I don’t want to scare you. It’s not that Chocolate Caramel Shortbread, known as Millionaire’s Shortbread in the UK, is hard recipe. Although it has three separate components, they are actually simple to make. But you must read and follow the directions carefully, or you could face an epic mess.

The first time I tried to make these bars, I skimmed over the directions and thought I had it down. I therefore missed a crucial step. Unlike other caramels, which cook the sugar first and add any dairy at the end, this filling includes two kinds of dairy that are added at the start of cooking. Therefore, you must stir the mixture almost the entire time.

I assumed the filling would cook like other caramels and barely stirred it, walking away frequently to do other tasks in the kitchen (another bad choice). By the time I realized it smelled like burning, it was too late. The caramel was horribly burnt. Not only was it unusable, it was scorched into a thick, black layer at the bottom of my lovely All-Clad pot! It took days of soaking and scraping to get it clean. Thankfully, the pot was saved!

So, learn from my mistakes — stir this filling almost constantly and do not walk away from the stove until it’s done! Because you definitely want to try this recipe. When I got it right on the second try, the cookies disappeared in mere days. They are essentially a gourmet, homemade Twix bar. Who wouldn’t want to try that?

An instant read thermometer works best here, as the temperature you need to hit for the caramel is hard to read on a traditional candy thermometer. You can see I started cooking the filling with mine, but I ended up taking it out and getting the final read using my Thermapen.

Chocolate Caramel Shortbread (Millionaire’s Shortbread)
Adapted from a recipe from Cook’s Illustrated 
Makes about 40 cookies

Shortbread crust

• 2 1/2 cups (12 1/2 oz) all-purpose flour
• 1/2 cup (3 1/2 oz) sugar
• 1 tsp kosher salt
• 1 cup (2 sticks) unsalted butter, melted

Caramel filling and chocolate topping

• 1 (14-oz) can sweetened condensed milk
• 1 cup (7 oz) brown sugar
• 1/2 cup heavy cream
• 1/2 cup corn syrup
• 1/2 cup (1 stick) unsalted butter
• 1/2 tsp kosher salt
• 8 oz bittersweet or semisweet chocolate

Preheat the oven to 350.  Make a sling for a 13 x 9 inch baking pan with two long sheets of aluminum foil. Lay sheets in pan perpendicular to each other, with extra foil hanging over edges. Push the foil into the corners and smooth the edges so its flush with the pan.

Mix the flour, sugar and salt in a medium bowl.  Add the melted butter and stir with a rubber spatula until flour is evenly moistened.  Crumble dough evenly over the bottom of the prepared pan.  With clean hands, press and smooth the dough into an even layer. Pierce the dough at 1-inch intervals with a fork.  Bake until light golden brown, 25-30 minutes.  Transfer pan to a wire rack.  Using a sturdy metal spatula, press on the entire surface of the crust to compact it (this will make the bars easier to cut later).  Let crust cool on the rack at least 20 minutes, until its just warm.

Stir together all the caramel filling ingredients in a large, heavy-bottomed saucepan. Cook over medium heat, stirring almost constantly, until mixture registers 236, 16 to 20 minutes. Pour over shortbread crust, and spread to even thickness (mixture will be very hot). Let cool completely, about an hour.

Finely chop 6 ounces of the chocolate; grate the remaining 2 ounces on the large holes of a box grater. (When a piece gets too small to safely grate, just toss it with the chopped chocolate). Microwave the chopped chocolate at 50 percent power for 15 second intervals, stirring thoroughly in between, until the chocolate is fully melted and smooth. Don’t overheat the chocolate; it should not be much warmer than body temperature when melted. Add the grated chocolate and stir until melted, microwaving at 50 percent power for 5 seconds if needed to complete the melting. Spread the meted chocolate evenly over the caramel filling with an offset spatula.  Refrigerate the bars until chocolate is just set, 10-20 minutes.

Lift the foil to remove shortbread from pan and transfer to cutting board (discard the foil). Using a serrated knife and a gentle sawing motion, cut shortbread in half crosswise to create two rectangles, then cut each in half again to create 4 strips. Cut each strip crosswise into equal pieces. Shortbread can be stored at room temperature, between layers of parchment, for up to one week.