Yield: 24 bars
Prep Time: 45 minutes
Cook Time: 40 minutes
Total Time: 1 hour 30 minutes
For the crust:
1¾ cups all-purpose flour
2/3 cup confectioners' sugar, plus extra for decorating finished bars
¼ cup cornstarch
¾ teaspoon salt
12 tablespoons (1½ sticks) unsalted butter, at cool room temperature, cut into 1-inch pieces, plus extra for pan
For the lemon filling:
4 large eggs, beaten lightly
1-1/3 cups granulated sugar
3 tablespoons all-purpose flour
2 teaspoons grated lemon zest, from about 2 large lemons
2/3 cup lemon juice
1/3 cup whole milk
Pinch of salt
1. Adjust an oven rack to middle position and preheat the oven to 350 degrees F. Lightly butter a 9x13-inch baking pan and line with one sheet parchment paper. Dot the paper with a bit of butter, then lay a second sheet of parchment paper crosswise over it.
2. Pulse flour, confectioners' sugar, cornstarch, and salt in a food processor. Add the butter and process for 8 to 10 seconds and then pulse until the mixture is pale yellow and resembles coarse meal, about three 1-second pulses. (To do this by hand, mix flour, confectioners' sugar, cornstarch, and salt in medium bowl. Freeze the butter and grate it on the large holes of a box grater into the flour mixture. toss the butter pieces to coat. Rub the pieces between your fingers for a minute, until flour turns pale yellow and coarse.) sprinkle the mixture into the lined pan and press firmly with fingers into an even ¼-inch layer over the entire pan bottom and ½-inch up the sides. Refrigerate for 30 minutes, then bake until golden brown, about 20 minutes.
3. Meanwhile, whisk the eggs, sugar and flour in a medium bowl, then stir in the lemon zest, lemon juice, milk and salt to blend well.
4. Reduce the oven temperature to 325 degrees. Stir the filling mixture to reblend; pour into warm crust. Bake until the filling feels firm when touched lightly, about 20 minutes. Transfer the pan to a wire rack; cool to near room temperature, at least 30 minutes. Transfer to cutting board, fold paper down, and cut into bars. Sift confectioners' sugar over bars, if desired. Leftover bars can be covered in plastic wrap and refrigerated for up to 2 days.
*Note: The filling needs to be poured into a warm crust straight from the oven, so once the crust is in the refrigerator chilling, prepare the filling so it's ready when the crust comes out of the oven.
(Recipe adapted from Cook's Illustrated)