2 1/2 cups all-purpose flour
1/2 cup sugar
3/4 teaspoon salt
16 tablespoons unsalted butter, melted
1 can sweetened condensed milk
1 cup packed brown sugar
1/2 cup heavy cream
1/2 cup corn syrup
8 tablespoons unsalted butter
1/2 teaspoon salt Chocolate
8 oz bittersweet chocolate (6 oz chopped fine, 2 oz grated)
For the Crust: Adjust oven rack to lower-middle position and heat oven to 350 degrees. Line bottom and sides of 13- by 9-inch baking pan with aluminum foil. Combine flour, sugar, and salt in medium bowl. Add melted butter and stir with rubber spatula until the flour is evenly moistened. Crumble dough evenly over bottom of prepared pan. Using your fingertips and palm of your hand, press and smooth dough into an even thickness. Using a fork, pierce dough at 1-inch intervals. Bake until light golden brown and firm to touch, 25 to 30 minutes. Transfer pan to wire rack. Using a sturdy metal spatula, press on the entire surface of warm crust to compress (compressing crust while warm will make cutting finished bars easier). Cool crust to just warm, at least 20 minutes.
For the Filling: Melt butter in medium saucepan over medium heat. Add sugar and cook, stirring constantly, until mixture is homogenous and sugar is melted 2 to 3 minutes. Stir in sweetened condensed milk, increase heat to medium-high, and bring to boil. Cook, stirring constantly and scraping corners of the saucepan, until mixture registers 235 degrees, 2 to 3 minutes. Remove from heat and stir in salt. Pour over crust and spread to even thickness. Let cool until filling is just warm, about 20 minutes.
For the Chocolate: Microwave 6 ounces chopped chocolate at 50 percent power, stirring every 15 seconds until fully melted but not much warmer than body temperature, 1 to 2 minutes. Add 2 ounces grated chocolate, and stir until melted, returning to microwave for no more than 5 seconds at a time to complete melting if necessary. Spread chocolate evenly over the surface of filling. Refrigerate shortbread until chocolate is just set, about 10 minutes. Let sit at room temperature for at least 1 hour before cutting.
Using foil, remove shortbread from pan and transfer to cutting board; discard foil. Using a serrated knife and sawing motion, cut shortbread in half crosswise to create two 6 ½- by 9-inch rectangles. Cut each rectangle in half to make four 3 ½ – by 9-inch strips. Cut each strip crosswise into equal 10 pieces. (Shortbread can be stored at room temperature, between layers of parchment, for up to one week.) I just cut mine into squares, so they are not too big, as they are quite rich. (but yummy)
I like to put on parchment paper on a cooking tray after cutting and separating the cookies to freeze, then you can keep them a bit longer.