St. Louis-Style Creamy Dreamy Butter Cake Squares

1. Setup

Position an oven rack in the upper-middle section and preheat your oven to 350 degrees Fahrenheit. Create a foil sling for a 13 by 9-inch baking pan by using two long sheets of aluminum foil – one should be the width of the pan, and the other the length. Arrange them perpendicularly, letting the excess hang over the edges for easy removal later. Press the foil into the pan's corners and sides, then coat with a non-stick vegetable oil spray.

2. Crust Foundation

In a mixing bowl, whisk together the flour, confectioners' sugar, and salt. Pour in the melted butter and blend with a rubber spatula until you have an evenly moistened mixture. Evenly distribute the dough crumbles across the bottom of your prepared pan. Firmly press it down into a uniform layer with the base of a dry measuring cup. Prick the surface with a fork approximately 20 times. Bake until the edges turn a light golden brown, which should take about 20 minutes. Let the pan cool on a wire rack for about 30 minutes until completely cool.

3. Creamy Filling

In the bowl of a stand mixer fitted with a paddle attachment, beat the softened cream cheese and butter on low speed. Gradually add sugar until it's fully incorporated, pausing to scrape the bowl's sides and bottom as needed. Increase the speed to medium-high, beating until the mixture becomes light and fluffy, which should take around 2 minutes. Lower the speed and add eggs and yolks one at a time, mixing well after each addition. Stir in vanilla extract and salt until just combined, scraping the bowl again as necessary. Boost the mixer to medium-high and beat the filling until it achieves the consistency of frosting, about 2 more minutes. Spread this creamy filling evenly over the cooled crust, tapping the pan on the counter lightly to expel any air bubbles.

4. Baking and Finishing

Place the pan into the oven and bake until the top is golden, the edges have cracked slightly, and the center jiggles a bit when the pan is nudged, roughly 30 minutes. Allow the pan to cool on a wire rack for at least 3 hours until it reaches room temperature. Use the foil overhangs to lift the cake out of the pan. Slice into 12 squares, dust with additional confectioners' sugar, and serve.