Happy Pi Day! This may be my favorite silly holiday ever and I usually take advantage of it to make something pie-related. But there’s been a lot of pie on this site already. So today, while there is crust and there is filling, it’s not really what you’d call pie. You’ll see.
I’ve mentioned before on this site that I could be called a lemonhead. I’m fairly addicted to anything puckering-ly tart. When a bakery has a pastry with lemon, nine times out of ten it will be my top choice. But that tenth time, the pasty is a lemon square and then I just can’t do it.
I love the idea of lemon squares but in execution, I often find myself disappointed. First, the crust: why must it always crumble? The crust of lemon squares is generally a short crust – somewhat similar to a tart but in the cookie form, it seems to just fall apart. Crumbs everywhere. My second problem is that the filling is generally too sweet. It’s more sugar than lemon which is not really the point. I’ve tried lemon squares at home a couple of times but they have the same problems. So I set out to fix it.
The first thing that had to go was the crust. This is supposed to be a cookie so I ditched the more doughy crust for a shortbread cookie. This solves the crumbly problem without really changing the flavor. The resulting base is much softer and it also soaks in a little lemon flavor from the filling.
And oh man, the filling. This was the real challenge. Lemon bar filling is not unlike lemon curd with eggs providing the structure. In order to make the bars set up properly, they need sugar to create a cooked texture, not unlike a jam. But the sugar also dulls the lemon flavor and therein lies my big problem – not-tart-enough-bars. I still needed the bars to bake up solid but in order to decrease the sugar, I needed to include some kind of thickener. The options were some kind of flour or cornstarch mixture to soak up the extra liquid or to use some kind of fat that would stay solid at room temperature so that it would set up as it cooled.
The flour/cornstarch didn’t appeal to me since it can add a weird flavor and texture to the resulting mixture. And I didn’t want to add butter since its creaminess can mute the tartness of the lemons. The key, I discovered, was sour cream. It provides the solidity as the bars set up but it doesn’t diminish the sourness.
Perhaps the best side effect of this experimentation is that the soft shortbread dough soaks up a little of the filling as it cooks and creates a kind of middle layer. Even topped with powdered sugar, they are pretty pucker and crumble free. A dessert phobic friend of mine had two the other night which may have been a first for him. And as for me, I’ve found a pretty perfect lemon pastry.
1 stick (8 tbs) butter, room temperature
1 cup confectioner’s sugar
½ tsp kosher salt
1 cup flour
2/3 cup lemon juice (about 4 medium lemons)
Zest of 4 lemons
½ cup sugar
½ tsp kosher salt
3 tbs sour cream, room temperature*
Additional confectioner’s sugar for dusting.
Preheat the oven to 350F and butter an 8 by 8 pan.
Cream the butter and sugar together on low speed until combined.** Turn the speed to medium until some air has been incorporated and the mixture lightens in color.. Add the salt and then the flour and mix on medium speed until the dough is crumbly. Add the egg and mix until smooth and well combined.
Spread the dough evenly in the pan and bake for 15 minutes until the edges are slightly brown but the top is still pale. Remove from the oven and let it cool to room temperature.
Preheat the oven to 375F.
Whisk together lemon juice, zest, sugar, and salt in a small bowl. In a medium bowl, whisk together the eggs and sour cream until well combined and no lumps of sour cream remain. Add the lemon and sugar mixture and whisk thoroughly. Pour the filling over the par-baked crust and bake for 20-30 minutes or until the filling is mostly set and barely jiggles in the center.
Let the bars cool completely before you cut them. Then dust them with confectioner’s sugar from sifter or fine-mesh strainer.
You can refrigerate the bars but the confectioner’s sugar will melt in the humidity of the fridge. Still delicious.
* Cold sour cream won’t mix in well and you’ll end up some specks of sour cream randomly throughout the finished product. It’s not bad per se, but it is a kind of weird flavor for that one bite. Letting the sour cream come to room temperature and whisking it thoroughly with the eggs will prevent this from happening to you.
** Combining confectioner’s sugar with butter on high speed will cause it to fly all over the kitchen. If you, like me, don’t like being covered in sugar dust, turn that speed down to low until the sugar is all mixed in.