Recipe and Tips: Lemon Curd
What’s in a name? How unfortunate that lemon curd is saddled with its. Curd suggests a texture of cottage cheese, doesn’t it? But lemon curd, made from lemons, sugar, butter, and sugar, is silky smooth and creamy and completely non-curdy. It’s an ideal mate for a crisp piece of toast, English muffin, or scone; a tangy filling for a cookie or tartlet; and a topping on a slice of spice or pound cake. Its uses are endless. It’s great to have on hand in the refrigerator or freezer. And the best part is lemon curd is easy to make.
There are two different ways to make lemon curd. The most common is to whisk the eggs, sugar, and lemon juice together, add the cold butter cut into small pieces, and stir everything together in a saucepan over a low heat until the butter melts and the whole mass thickens into a custard-like cream.
The other way is similar to making a cake. You beat the butter and sugar with an electric mixer until smooth and fluffy, beat in the eggs and juice and slowly cook the brew.
Which is best? Making lemon curd involves knowing a few things about egg cookery. The most important is to cook them slowly over a relatively low heat so that they thicken but don’t coagulate. Heat and acid excite molecules—in this case egg proteins—and make them want to interact with each other by coming together and bonding. The trick here is to delay the process so that the proteins don’t move about so quickly that they crash into each other and coagulate—as happens when you fry an egg.
One way to slow down the egg protein interactions is by using low to medium heat. Another is by introducing other molecules that get in and mingle with the egg proteins to protect them. Sugar and fat, for example.
In the first method for making lemon curd, the eggs are whisked with the sugar and juice, but the butter is added later.
In the second method, both sugar and butter are beaten with the eggs, giving them a double layer of protection right from the start. My money’s on method 2.
And beating vigorously with a mixer denatures the proteins in the eggs so that they won’t curdle as easily as eggs merely whisked. This picture shows the butter creamed with the sugar.
After beating in the eggs, the mixture becomes very smooth.
For best results, follow these tips.
Use a heavy-bottomed saucepan. Stainless steel, enameled iron or anodized aluminum are all excellent. Don’t use plain aluminum because it reacts with acids in lemon, discolors the curd, and gives it a metallic taste. A large pan is better than a small one to give you ample room to stir the curd.
Use a heatproof rubber spatula and whisk. I use the spatula for most of the cooking and switch to the whisk near the end just to make sure the curd is smooth.
Stir the curd often as it cooks. Make sure to move your spatula or whisk constantly at a moderate speed all over the bottom, sides, and seam of the pan. Keeping the eggy liquid in motion allows you to control the coagulation reaction. You want it to be slow and gentle so that the curd becomes creamy and smooth, not solid.
Watch that heat! Make absolutely certain the curd never reaches the boiling point. The curd will set at 170˚F. I highly recommend you have a digital probe thermometer to check the curd temperature. Once the curd has set it will thicken further as it cools.
Now you’re ready to begin.
4 ounces (1 stick) unsalted butter, slightly softened
1 ½ cups sugar
Finely grated zest of 2 lemons (about 4 teaspoons)
3 large eggs
2 large egg yolks
2/3 cup fresh lemon juice
Pinch of salt
Beat the butter until very smooth with an electric mixer. While beating on medium-low speed, gradually add the sugar. When all the sugar is in, scrape the bowl and beater, add the lemon zest, and beat 2 to 3 minutes on medium speed until fluffy.
Beat the eggs and yolks with a fork to combine. On medium-low speed, dribble in the eggs and beat until very smooth, about 1 minute.
On low speed, gradually add the lemon juice (try not to splash) and the salt. The mixture will probably look a bit curdled. Don’t be alarmed; it will become smooth during cooking.
Scrape the sauce into a medium-to-large heavy-bottomed saucepan (3 to 4-quarts is a good size).
Set the pan over medium-low heat and stir constantly with a heatproof rubber spatula making sure to go all over the bottom, sides, and junctions of the pan. Remember, you’re cooking eggs, and if they overheat they’ll scramble. Just stir constantly and you’ll be fine. If you get nervous about cooking lemon curd over direct heat, set your saucepan into a larger pan (say, 12-inch skillet) with about an inch of barely simmering water.
As the curd heats it first thins out because the butter melts, then as the egg proteins unite, the curd transforms into a thick custard-like sauce. It takes about 10 minutes for the curd to thicken properly. If at any point you see the curd turning lumpy, immediately remove the pan from the heat and whisk the curd until smooth.
The curd is close to being done when you see wisps of steam rising from its surface. It’s cooked when you swipe a finger on the curd-coated spatula and the path remains clear.
This is exactly what happens when you make a crème anglaise. The temperature on a digital thermometer will read 170˚F.
Scrape the curd into a bowl and press a piece of plastic wrap directly on its surface to keep a skin from forming. Refrigerate. It will thicken even more as it cools.
Lemon curd keeps well refrigerated for at least 1 week. It may also be frozen for up to 1 month.
Makes about 3 cups.
Here’s a lovely way to serve lemon curd, spooned into a glass and topped with whipped cream, raspberry sauce, and a fresh raspberry.