Espresso Millionaire Bars

Ingredients

• Baking spray with flour
• 10 tablespoons unsalted butter, softened
• 1/3 cup granulated sugar
• 1/4 teaspoon fine sea salt
• 1 1/4 cups all-purpose flour (about 5 3/8 ounces)
• 1 1/2 tablespoons Dutch-process cocoa
• 1 1/4 cups granulated sugar
• 1/4 cup water
• 1 teaspoon light corn syrup
• 1 (14-ounce) can sweetened condensed milk
• 1/4 cup unsalted butter
• 1 tablespoon instant espresso powder
• 1/4 teaspoon fine sea salt
• 5 ounces dark chocolate (70% cacao), finely chopped (about 1 cup)
• 2 tablespoons heavy whipping cream
• 1 tablespoon unsalted butter, softened
• 4 ounces white chocolate, finely chopped (about 1/2 cup)
• 1 1/2 teaspoons coconut oil
• Gel food coloring

Steps

1. Make the crust: Preheat oven to 350°F. Coat a 9-inch square baking pan with baking spray; line pan with parchment paper, leaving a 2-inch overhang on all sides. Coat parchment paper with baking spray, and set aside.
2. Mix together butter, sugar, and salt in a medium bowl using a spatula until smooth and creamy. Add flour and cocoa; stir until mixture just comes together into a rough dough. Spread dough into prepared baking pan; cover using plastic wrap, and press firmly using your fingers or the bottom of a glass to form an even layer.
3. Bake crust until set, 20 to 25 minutes. Cool completely in baking pan on a wire rack until crust is firm, about 1 hour.
4. Make the caramel: Combine sugar, 1/4 cup water, and corn syrup in a medium saucepan, stirring gently to avoid splashing the sides of the pan. Cook over high, without stirring or moving the pan, until mixture begins to turn amber along the edges, 5 to 10 minutes. Swirl pan gently, allowing the mixture to evenly caramelize. Continue to cook until caramel is a dark amber, 30 seconds to 3 minutes more. Remove pan from heat; carefully whisk in condensed milk, butter, espresso powder, and salt. Return saucepan to stovetop, and cook over medium-low, whisking constantly, until caramel registers 225°F to 230°F on a candy thermometer, 3 to 8 minutes. Immediately spread caramel over cocoa crust; cool to room temperature, about 2 hours.
5. Make the topping: Place dark chocolate, cream, and butter in a small microwavable bowl; microwave on high in 15- to 30-second intervals, stirring between each interval, until smooth and well combined, 30 seconds to 2 minutes. Place white chocolate and coconut oil in a separate small microwavable bowl; microwave on high in 15- to 30-second intervals, stirring between each interval, until smooth and melted, about 1 minute. Divide and tint white chocolate with desired gel food colors.
6. Spread dark chocolate ganache in an even layer over caramel mixture in baking pan. Dollop and drizzle melted white chocolate over top; swirl chocolates together using the tip of a knife or skewer. (Alternatively, chill chocolate ganache layer for 10 minutes before adding white chocolate to prevent ganache from showing through.) Tap baking pan on the countertop several times to remove any large air bubbles. Chill until set, about 1 hour.
7. Lift the entire shortbread from the baking pan using parchment paper overhang as handles. Dip a thin, sharp knife in hot water to warm the blade; wipe knife dry, and cut shortbread (cleaning knife as needed) into bars. Serve cookies at room temperature.