Gooey Butter Cake

Ingredients

• Cooking spray
• 1 cup (about 4 1/4 ounces) all-purpose flour, plus more as needed
• 1/4 cup granulated sugar
• 1/2 teaspoon kosher salt
• 1/2 cup (4 ounces) cold unsalted butter, cubed
• 1 large egg, lightly beaten
• 3/4 cup (6 ounces) unsalted butter
• 1 cup packed light brown sugar
• 1 large egg
• 1 1/2 teaspoon vanilla extract
• 1 cup (about 4 1/4 ounces) all-purpose flour
• 2/3 cup evaporated milk (from 1 [12-ounce] can)
• 1/4 cup light corn syrup
• Flaky sea salt

Steps

1. Heat the oven to 350°F. Lightly spray an 8-inch square baking pan with cooking spray and line it with parchment paper.
2. Whisk the flour, sugar, and salt in a large bowl. Cut in the butter cubes with 2 forks or a pastry blender until crumbly, then stir in the egg to make a rough dough. Gather into a ball with your hands and put in the prepared pan. Use your hands or a rubber spatula to press it evenly across the bottom, flouring your hands as needed. Chill until needed.
3. Melt the butter in a small saucepan over medium-low heat. Cook for about 10 minutes, stirring occasionally, until it starts foaming and turns brown. Immediately pour into a heatproof glass bowl, cover, and chill for about 1 hour, until solidified. For faster cooling, put it in a freezer-proof bowl and freeze for about 30 minutes. If needed, set the bowl of solidified butter in a large bowl of warm water for 10 seconds.
4. Using a stand mixer with a paddle attachment, beat the butter and brown sugar on medium speed for about 3 minutes, until fluffy. Lower the speed to low, add the egg and vanilla, and beat for about 30 seconds, until combined, stopping to scrape the bowl sides if needed. On low speed, add the flour and evaporated milk alternately until just incorporated, about 1 minute. Beat in the corn syrup for about 15 seconds, until combined.
5. Spread the filling evenly over the crust in the prepared pan. Bake in the preheated oven for 40 to 45 minutes, until the top is golden brown and the center almost set. Take out of the oven and sprinkle flaky sea salt evenly on top. Cool at room temperature for about 1 hour, cut into squares, and serve at room temperature.