Welcome to Baking 1-2-3, by associate food editor Claire Saffitz. Each month, she'll guide you through a three-step baking process. The first recipe is for the beginners out there, the second for intermediate-level bakers, and the third recipe is for the experts. Today...lemon curd!
Lemon curd is one of the first things I remember cooking when I was old enough to use the stove without supervision. I looked up a recipe in my one of my mom’s Martha Stewart cookbooks and went to work, stirring anxiously and monitoring closely for signs that the mixture was thickening so as not to curdle the eggs. My carefulness paid off because the end result was a marvel—smooth, silky, and puckeringly tart. I was in love.
Years later, one of the first recipes I ever made as a pastry cook in my first restaurant job was lemon curd. That recipe was dressed up with the addition of real vanilla bean, ginger, and fresh butter from Normandy, but the basic method was the same: eggs, sugar, and lemon juice cooked until thick, mounted with butter, and then cooled. It’s a versatile recipe to say the least, forming the base of desserts from the humble lemon bars of your childhood to the most elegant of tarts. Here, I give three recipes based around lemon curd and its many uses: a simple no-fuss bar, then a slightly more complicated baked version, and an impressive pie.
Lemon curd is a basic custard, meaning it’s thickened by eggs. Although many curd recipes call for just yolks, I prefer to use a combination of whole eggs and yolks to add a bit of lightness. Lemon curd is also a stirred custard, which means it’s agitated as it cooks (as opposed to still custards, which are baked—think crème brûlée). Stirred custards continue to thicken as they cool but never set as firmly as a baked custard. This is why unbaked lemon bars have a slightly looser lemon filling and should therefore be served cold from the fridge.
When baking lemon squares (or lemon pie), the curd gets a firmer set and is very stable at room temperature. Making a stirred custard and then baking it has its advantages; it doesn’t require thickeners like cornstarch or flour in addition to eggs, which results in a pie with a cleaner, brighter flavor than a typical lemon pies.
The baked lemon pie recipe also includes a marshmallow topping. True marshmallow—and I’m not talking about those ones from a bag—is nothing more than an Italian meringue set with gelatin. The end result is essentially a lemon meringue pie that can sit out or in the fridge for a day or more without weeping. This method also allows you to work in stages, making the pie the day before, topping the cold pie with marshmallow in the morning and letting it set, and then browning before serving. It’s nearly foolproof and superior in flavor to any other lemon meringue pie I’ve tried. At any level, it’s worth trying. You can go all in or, if you want to just make the curd and eat it from a spoon, that’s okay too.
Make the crust according to the recipe. Firmly press dough into an 8x8" baking dish, working about ½" up the sides (the firmer you press, the easier it will be to cut the baked crust). Bake until golden brown on bottom and a shade or two darker at the edges.
If making unbaked lemon bars, wait until the crust has cooled completely before adding the prepared and strained curd and spreading it to the sides of the crust.
For unbaked bars, chill until set, about 1 hour, before serving cold.
If making baked lemon bars, start the curd just before the crust is finished baking so that both are warm when you assemble. Strain warm curd through a sieve into warm crust and bake until curd is set around the edges (filling should still wobble when dish is jiggled). Do not overbake or filling may curdle. Transfer to a wire rack and let cool, then chill until cold, at least 1 hour. Just before serving, cut lemon bars into squares and dust with powdered sugar.
Prepare and bake the crust per normal. Begin to prepare the curd while the crust is baking. Remove the crust, and reduce oven temperature to 300˚. Strain warm curd through a fine-mesh sieve into warm crust, filling right to top of crust (do not overfill; you may have a tablespoon or so extra).
Bake pie until curd is set around the edges (filling should still wobble when dish is jiggled; it will continue to set as it cools), 15−20 minutes. Do not overbake or filling may curdle.
Make sure curd is chilled and set before adding the marshmallow topping. Marshmallow topping will become difficult to work with if given time to set up, so immediately (and quickly) ____ dollop spoonfuls of marshmallow over curd, swirling and making decorative swoops as you go (make sure to extend topping all the way to edge of crust).
Let sit until marshmallow is set and firm, at least 2 hours and up to 6 hours.
Just before serving, heat broiler. Broil pie until marshmallow is toasted and golden brown in spots (keep a close eye on it to keep it from burning), about 2 minutes.