Recipe adopted from The New Best Recipe. [Recipe makes 16 bars].
This was my first time giving America's Test Kitchen's recipe a try, and I don't think I'd change a thing. The crust is thicker than most recipes, and is a crisp shortbread rather than the usual pie crust. [Side note: If you prefer a softer crust, I recommend the alterations that Mel made on her blog]. The filling is thick enough to hold its shape, but is soft enough to compliment the texture of the shortbread. What I liked most about this recipe is the fact that the filling had the perfect balance between the lemons and sugar without it being too tart or too sweet. You'll want to give the recipe a full read-through ahead of time since timing is more crucial than most recipes, but I guarantee it's very easy to follow and will give you the best lemon bars you've ever had.
6 1/4 ounces (~1 1/3 cup) all-purpose flour
2 ounces (~1/2 cup) powdered sugar
1/2 teaspoon table salt
8 tablespoons (1 stick) unsalted butter, cut into 1-inch pieces and softened yet cool
7 large egg yolks plus 2 large eggs
7 7/8 ounces (~1 cup plus 2 tablespoons) sugar
3/4 cup freshly squeezed lemon juice (from 4 to 5 large lemons)
1/4 cup finely grated lemon zest (from 4 to 5 large lemons)
Pinch of table salt
4 tablespoons unsalted butter, cut into 4 pieces
3 tablespoons heavy cream
For the crust, spray a 9-inch baking pan (preferably glass) with cooking spray. In a food processor, combine the flour, powdered sugar, and salt until combined. Add the butter and process for up to 10 seconds, or until the mixture is mealy. Transfer this mixture to the baking pan, and press down with your fingers or a flat-bottomed cup until the base is uniform in thickness and firm. Transfer to the refrigerator for 30 minutes. While the base is cooling, preheat your oven to 350° F. Once 30 minutes have passed, bake the crust for 20 minutes, or until golden brown.
While the crust is baking, prepare the filling. [Side note: Since the crust should be hot when you add the hot filling to it, plan on finishing the filling around the same time that the crust comes out of the oven]. Start by whisking together the yolks and eggs in a non-reactive bowl until combined. Add the sugar and whisk until combined. Add the fresh lemon juice, zest, and salt, and whisk until combined. Transfer the lemon mixture to a non-reactive saucepan, add the butter, and cook over medium-low heat. Stir constantly until the lemon curd registers 170° F. For those without an instant-read thermometer, this will take place after 5 to 7 minutes, or until the mixture just starts to thicken. Remove from the heat and pour the mixture through a sieve. This will remove the lemon zest and any egg that might have cooked too fast. Stir in the heavy cream.
Spread the sieved mixture over the browned crust, and return the pan into the oven for another 10 minutes, or until the center-third is still jiggly when the pan is gently shaken. Let the bars rest on a cooling rack for an hour, and then transfer to the refrigerator for at least 3 hours (or overnight) to finish cooling.