Salted Cookie Butter Millionaire's Shortbread | Jesse Szewczyk

<p>Cook along with Jesse Szewczyk to make these crunchy, perfectly spiced, and understated shortbread cookies that are as delicious dunked into hot coffee as they are eaten all on their own.</p><p><a href="https://food52.com/recipes/88660-millionaires-shortbread-cookie-butter-recipe?preview=true"><strong>Recipe</strong></a><br />Makes 24 bars<br /> </p><p><i>Shortbread Base</i></p><ul><li>1 2/3 cups (214g) all-purpose flour</li><li>1/3 cup (67g) granulated sugar</li><li>1/2 teaspoon kosher salt</li><li>12 tablespoons (1 1/2 sticks/170g) unsalted butter, melted</li><li>1 large egg yolk</li><li>1 teaspoon vanilla extract</li></ul><p><i>Salted Speculoos Caramel</i></p><ul><li>3/4 cup (175 grams) packed light brown sugar</li><li>4 tablespoons (1/2 stick/57g) unsalted butter</li><li>1/4 cup (59 ml) light corn syrup</li><li>1 14-ounce can (414 ml) sweetened condensed milk</li><li>1/3 cup (90 grams) speculoos cookie butter (see Note)</li><li>1 teaspoon vanilla extract</li><li>1 teaspoon kosher salt</li></ul><p><i>Topping</i></p><ul><li>1/2 cup (about 3 ounces/85 grams) semisweet chocolate chips</li><li>1/2 cup (about 3 ounces/85 grams) white chocolate chips</li><li>4 tablespoons (59 ml) whole milk, divided</li><li>2 tablespoons (36 grams) speculoos cookie butter, divided</li><li>Flaky sea salt, for sprinkling</li></ul><ol><li><i>Make the shortbread base</i>: Heat the oven 325°F. Grease an 8- by 8-inch baking pan with nonstick pan spray and line with parchment paper, leaving overhang on all four sides. In a large bowl combine the flour, granulated sugar, and salt. Add the melted butter, egg yolk, and vanilla extract and stir together until a soft dough forms. Transfer the dough into the lined baking pan and press into an even layer. Prick the top several times with a fork and bake until the shortbread is slightly puffed and golden brown in the center, 33 to 38 minutes. Remove from the oven and use the bottom of a measuring cup or a metal spatula to press down on the shortbread to compact it slightly. (This will prevent t