The Crust
I knew that flour, butter, and sugar would be the main ingredients of the bottom layer. I also knew that since I wanted a cookie or shortbread texture rather than a pastry-type crust, I would need a fair amount of sugar. No liquid would be necessary because I wasn’t trying to create the little pockets of steam that produce flakiness and layering in pastry.
My first challenges were to decide the proportion of flour to butter and the amount, as well as the type, of sugar. I decided, after several taste tests, that a crust made with ½ cup of butter per
1 cup of flour resulted in a crust that was too rich, a little greasy, and not quite sturdy enough to cut. Cutting back to 1/4 cup, however, produced a crust that was hard and dry and crumbled when cut. An amount between these two—just over 1/3 cup of butter per cup of flour—proved to be just right.
Since sugar affects tenderness as well as sweetness, the amount and type of sugar needed to be determined along with the butter. Brown sugar proved too rich for my tasters’ palates, while granulated sugar produced a crust that was a bit brittle and gritty. The best, most tender texture came from confectioners’ sugar. To achieve the delicate crumb and melt-in-your-mouth quality of shortbread, I also added a bit of cornstarch to my formula.
Having decided on the basic ingredients, I began to investigate ways to combine and bake them. For most cookies and one type of pastry, the fat and sugar are creamed together in the first step. The alternative is to start by cutting the fat into the flour with your fingertips or a food processor, which is common in most pastry crusts. After testing both methods, I decided that because of the proportion of flour to butter and the absence of liquid, the second method was best suited for this crust. Cutting the butter into the flour created a crumbly mixture that could be pressed into the pan. To insure an evenly baked crust and prevent sogginess, I found it necessary to prebake the crust and discovered, through trial and error, that the standard temperature of 350 degrees worked best.
Once I had decided on a formula and the best techniques for making the bottom layer, all that remained was to discover the right proportion of crust to filling. The bottom layer must not only provide support for the topping but also balance the lemony taste. A crust that was about 1/4-inch thick provided the right foundation for the amount of filling I wanted, which ended up being about 1/3 inch in depth.

The Lemon Layer
The usual method for making the lemon layer of these sweet bars is to mix eggs, sugar, lemon, and flour, pour it over the prebaked crust, and bake until set. But before trying this, I took a detour—I spread a precooked lemon filling over the prebaked crust and allowed it to set. This method worked only passably well because it required a filling that was made with butter and thickened with cornstarch, which turned out to be dull and a bit gummy.
Returning to the original method of baking, I proceeded to discover the amount of fresh lemon juice I would need for a clear, tart lemon flavor. I knew that 2 tablespoons of lemon juice, the minimum amount in the recipes I had researched, would not produce the zing that I was after, and initial tests proved this to be true. The flavor was bland and uninteresting. I kept adding more, and eventually ended up with 11 tablespoons of juice and 2 teaspoons of zest. Even tasters who initially thought that this was too lemony ended up liking it. The 11 tablespoons of juice also provided enough liquid for a topping that was attractively light.
However, I eventually decided that I wanted a topping that was just a little less intense, so I tried replacing some of the lemon juice with other liquids. Water thinned it out too much, and heavy cream not only adversely affected the lightness, but also cut the lemony taste. Adding a small amount of whole milk, though, seemed to balance the flavor with the texture. I also found that baking the topping at a slightly lower temperature than was used for the crust (325 degrees rather than 350 degrees) helped produce the smooth texture I wanted, since eggs do not curdle when cooked at lower temperatures.
In my first round of tests, I thought it was unnecessary to thicken the filling with flour, which I wanted to avoid because I had detected its starchy taste in mixtures that had a high proportion of it. After more tests, though, I discovered two very good reasons to use it. First, some of the fillings baked without flour seemed to have a mealy texture after cooling, a result of the eggs being exposed to the oven heat during baking. Second, toppings made without flour became watery after sitting for only an hour or so. Adding just a small amount of flour solved both these problems without adding any starchy taste — buffering the eggs produced a smooth texture and effectively halted the “weeping.”
To investigate thickening properties a bit more, I tried adding an extra egg yolk in one test and cornstarch in a few others. The additional yolk produced a bright yellow color, a heavier texture, and an unwanted eggy taste. Cornstarch also yielded surprisingly negative results. The cornstarch filling did not thicken well because cornstarch cannot withstand high heat for an extended amount of time. But what surprised me most was the taste. Not only could you detect the starch on your tongue, you could also find its strong, metallic flavor in the filling.
Now I had only one last problem to solve. During all my tests, the filling would inevitably shift and stick to the the sides of the pan, which made it difficult to cut the bars along the edges. I solved this problem by lining the pan with paper, either parchment or waxed, the sides as well as the bottom. I cut two pieces to fit the pan, one for each direction, and held them in place with a small amount of butter. After baking, I lifted the uncut lemon bars from the pan by holding onto the edges of the paper. Because the paper could be cut or peeled away from the sides of the bars and there was no obstruction from the pan edges, I found it easy to cut them into even, presentable pieces, using either a knife or a large pizza wheel. A sifting of powdered sugar, and I had my lemon bars.

PERFECT LEMON BARS
Makes about two dozen 11/2- to 2-inch squares

The lemon filling must be added to a warm crust. The 30-minute chilling and 20-minute baking of the crust should allow plenty of time to prepare the filling. If not, make the filling first and stir to blend just before pouring it into the crust. Any leftover bars can be sealed in plastic wrap and refrigerated for up to two days.

The Crust
1 3/4 cups all-purpose flour
2/3 cup confectioners’ sugar, plus extra to decorate finished bars
1/4 cup cornstarch
3/4 teaspoon salt
12 tablespoons unsalted butter (11/2 sticks), at very cool room temperature, cut into 1-inch pieces, plus extra for greasing pan

Lemon Filling
4 large eggs, beaten lightly
11/3 cups granulated sugar
3 tablespoons all-purpose flour
2 teaspoons finely grated zest from
two large lemons
2/3 cup juice from 3 to 4 large lemons, strained
1/3 cup whole milk
1/8 teaspoon salt

1. For the crust: Adjust oven rack to middle position and heat oven to 350 degrees. Lightly butter a 13-by-9-inch baking dish and line with one sheet parchment or wax paper. Dot paper with butter, then lay second sheet crosswise over it (see illustration 1, "Making The Lemon Bars" PDF, below).
2. Pulse flour, confectioners’ sugar, cornstarch, and salt in food processor workbowl fitted with steel blade. Add butter and process to blend, 8 to 10 seconds, then pulse until mixture is pale yellow and resembles coarse meal, about three 1-second bursts. (To do this by hand, mix flour, confectioners’ sugar, cornstarch, and salt in medium bowl. Freeze butter and grate it on large holes of box grater into flour mixture. Toss butter pieces to coat. Rub pieces between your fingers for a minute, until flour turns pale yellow and coarse.) Sprinkle mixture into lined pan and, following illustration 2,("Making The Lemon Bars" PDF), below, press firmly with fingers into even, 1/4-inch layer over entire pan bottom and about
1/2 inch up sides. Refrigerate for 30 minutes, then bake until golden brown, about 20 minutes.
3. For the filling: Meanwhile, whisk eggs, sugar, and flour in medium bowl, then stir in lemon juice, milk, and salt to blend well.
4. To finish the bars: Reduce oven temperature to 325 degrees. Stir filling mixture to reblend; pour into warm crust. Bake until filling feels firm when touched lightly, about 20 minutes. Transfer pan to wire rack; cool to near room temperature, at least 30 minutes. Following illustrations 3 and 4, ("Making The Lemon Bars" PDF,) below, transfer to cutting board, fold paper down, and cut into serving-size bars, wiping knife or pizza cutter clean between cuts, as necessary. Sieve confectioners’ sugar over bars, if desired.

May, 1998


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Original article and recipes by Susan Logozzo