Instructions

• Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper so two opposite sides overlap, and spray the parchment and any exposed pan with nonstick baking spray; set pan aside.
• In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl using a handheld electric mixer, beat 1/2 cup unsalted butter (room temperature), 1/4 teaspoon almond extract, 1/4 cup confectioners' sugar, and 1/4 teaspoon salt until light and fluffy, about 2 to 3 minutes.
• Gradually add 1 cup all-purpose flour and mix on low just until combined; the dough will be a bit crumbly.
• Dump the mixture into the prepared pan and press it firmly and evenly into the bottom of the pan (use your fingers, the back of a spatula, or the bottom of a measuring cup) to form an even layer.
• Bake on the middle rack for 13 to 15 minutes, or until the shortbread is lightly browned. Remove from the oven and set the pan aside to cool until the shortbread is no longer hot to the touch and is at least warm or room temperature.
• While the shortbread cools, combine 16 ounces chopped semi-sweet chocolate, the (14-ounce) can sweetened condensed milk, and 1 tablespoon unsalted butter (cut into small bits) in a microwave-safe bowl.
• Microwave the chocolate mixture uncovered on low in 30-second increments, stirring after each increment, until the chocolate is completely melted and the mixture is smooth.
• Stir 3/4 teaspoon almond extract into the melted chocolate mixture.
• Spread the chocolate mixture evenly over the cooled shortbread with a spatula. Sprinkle 1/3 cup toasted sliced almonds over the top and press them down slightly so they adhere.
• Refrigerate the pan until the topping is firm, about 2 hours. Use the parchment overhang to lift the bars from the pan, then cut into small squares and serve.