Lemon curd is so delicious, so luscious, and so versatile that I’m sure it’s what all good lemons aspire to be when they grow up. We can thank the English for this bright yellow curd with its tart, vibrant flavor, as well as for the wonderful notion of spreading it on scones hot out of the oven.
Made by gently cooking a mixture of fresh lemon juice, sugar, butter, and eggs until thickened, lemon curd is also divine on buttered toast, a simple and perfect way to appreciate the curd’s cool, satiny texture. It makes an easy and delicious filling for tarts, cakes, and cookies. And a dollop of lemon curd tastes delicious with a piece of gingerbread or a slice of pound cake; its tart lemon flavor counters the spiciness of the former and the sweet richness of the latter. Pair it with a piece of thick Scottish shortbread and you’ll appreciate how lemon curd can transform a simple, somewhat homely cookie into something wonderful.
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A foolproof method makes the smoothest lemon curd
Lemon curd is easy to prepare, except for one pesky problem: it sometimes winds up with bits of cooked and curdled egg. This problem is especially common in curds that use whole eggs as well as egg yolks. Because the eggs whites cook at a lower temperature, they’re more prone to coagulation. These cooked bits don’t ruin the flavor of the curd, but a smooth texture will require careful straining, and quite a bit of the mixture can get lost in the process. It’s also rather alarming, especially for the uninitiated, to see those white lumps form during cooking.
For years I tried to find a method that eliminated the need for straining the curd. I tried cooking the sauce in a double boiler, cooking it in a heavy saucepan, adding some of the hot liquid to the eggs to temper them, whisking the mixture, using more eggs, using fewer eggs. I thought of eliminating the whole eggs altogether and using just the yolks as some cooks do (since the whites are more troublesome), but I prefer the lighter, almost custardy results I get from using whole eggs. When I finally found the answer, it wasn’t in my kitchen. It was at my hair salon.
I was getting my hair cut when my hairdresser, Mary Jane, told me that when she made my recipe for lemon curd, it didn’t need any straining. There were none of the cooked egg-white particles I had warned her about. As she cut my hair, we went over how she made the curd. By the time we were finished, I had a new recipe for lemon curd as well as a new haircut.
Instead of simply combining the ingredients in the pan on the stove as most lemon curd recipes call for, Mary Jane mixed the ingredients as if she were making a cake. She creamed the butter and sugar until fluffy, beat in the eggs slowly, and only then did she add the lemon juice. The method works every time: the curd thickens properly, becomes satiny-smooth, and there’s not one drop of cooked egg to strain.
The scientific secrets to the method
Why does this method for making lemon curd work so well? Successful lemon curd is the result of battling forces that encourage and discourage the eggs to coagulate. You want the eggs to thicken — but not too much, and not too soon.
Heat encourages the proteins in eggs to bond, as does the addition of acidic ingredients. Diluting the eggs raises the temperature at which coagulation begins, simply because it keeps the protein molecules in the eggs physically farther apart. According to food scientist Harold McGee, one tablespoon of sugar is enough to surround each protein molecule in a large egg with a screen of several thousand sucrose molecules.
But many recipes for lemon curd begin by beating the eggs with the sugar. What sets this one apart is the early addition of the fat. “What we cood have here is that the butter is coating the protein molecules pretty well,” says food scientist and Fine Cooking contributing editor Shirley O. Corriher. The coating of fat helps protect the eggs from the acid in the lemon juice.
The electric mixer gives you further insurance, adds Corriher. The vigorous beating denatures the proteins in the eggs, partially “cooking” or tempering them so that they won’t curdle as easily when heated.
A few tips for best results
With the right utensils and technique, you can make perfect lemon curd every time.
Use a heavy-based, nonreactive saucepan
Stainless steel, anodized aluminum, and enamel all work well. Some materials, such as plain aluminum or unlined copper, will react with the acid in the lemons, discoloring the curd and giving it a metallic flavor.
Stir the sauce often to keep it creamy and to prevent burning
Stirring the mixture keeps the protein molecules in the eggs from bonding too tightly, resulting in a creamy, rather than solid, curd. Be sure to scrape the spoon along the seam where the bottom and the sides of the pot meet — an area prone to burning.
Don’t let the curd boil
Boiling can cause the curd to curdle. Take your time and keep the heat moderate. Eventually the curd will thicken to the proper consistency. The curd is cooked when it reaches 170°F, but you can see that it’s cooked when your finger leaves a clear path on the back of a spoon (see photo at right). The curd will continue to thicken as it cools. For a double recipe, use a large saucepan and allow for additional cooking time.
Lemon curd freezes well
Tightly covered, lemon curd will last about a week in the refrigerator. Because I always like to have some lemon curd on hand, I often make a batch and freeze it; it will last for months tightly covered in the freezer. It doesn’t freeze solid, which means you can spoon out exactly what you need when you need it.
Finally, though lemon curd is my favorite, I also enjoy curd made from limes, which make a soft, cream-colored curd with flecks of green zest.
Five great ways to enjoy lemon curd
Make pretty sandwich cookies using lemon curd. Macaroons, butter cookies, and nut wafers all taste great with lemon curd spread between them.
Swirl lemon curd into cheesecake. Spoon a cup of room-temperature lemon curd in drops over an unbaked cheesecake. Use a butter knife to cut the curd into the cake to marbleize is before baking according to your recipe.
Fill tiny tarts with lemon curd. Bake your favorite butter pastry in mini muffin tins. Fill the baked tart shells with cold lemon curd and top with berries and cream. You can also bake the filled tarts for 15 minutes in a 325°F oven. Baking the curd firms the custard and gives it a deep golden color. These, too, may be topped with whipped cream or a light dusting of confectioners’ sugar.
Spread lemon curd between the layers of a cake. For a double lemon flavor, top the cake with a fluffy icing made by beating a cup of heavy cream and a teaspoon of vanilla extract until the cream begins to thicken, and then beating in a cup of cold lemon curd until the cream forms soft peaks.
Make a pretty lemon parfait. In a clear dessert bowl or glass, alternate layers of frozen lemon curd with the whipped cream-lemon curd mixture described above. Or substitute vanilla ice cream for the cream-curd mixture to make a lemon curd sundae.