Homemade lemon curd is an absolute treat, and once you make your own, you will never want to buy store-bought again. This curd is thick, tangy, creamy, and sweet, Try it on desserts from cakes, cupcakes, pies, tarts, macarons, ice creams, and more.
Measure all ingredients before you start. Cut the butter into cubes - keep chilled.
Juice the lemons - Place lemons in the microwave for 10 seconds before you cut and squeeze this will make it easy. Warm the lemon juice for about 30 secs - set aside
Use a double boiler or make your own - To make your own add an inch of water to the saucepan with a heatproof bowl on top. The water should not touch the top bowl.Tip - we use a double-boiler to prevent the eggs from getting scrambled with direct heat.
In the top bowl of your double boiler - add yolks, egg, salt, cornstarch, and sugar. Whisk until light and fluffy - sugar should almost melt.
Gradually pour in the warm lemon juice and zest. Now place the bowl on the double boiler.
Continue to stir on medium-high heat. The mixture should cook with just the steam from the water in the saucepan below.Tip - if you cook on low it will take forever to thicken. Since we are cooking on a double boiler you can keep the heat medium-high and stir continuously.
After about 10 to 12 minutes - you will notice the foam that was caused by whipping the egg mixture will slowly disappear. The mixture will start to thicken.
Continue to stir until it coats the back of your wooden spoon. Remove from heat.
Gradually add cubes of butter one at a time. Make sure each piece is well incorporated. The mixture will continue to thicken as it cools.Tip - the cool butter stops the cooking and makes it smooth and velvety. Add it slow but not too slow or the last of the butter won't incorporate in cooled curd.
Once all the butter has been incorporated, strain it through a mesh or a strainer to remove the zest. This will also give you a smooth creamy curd.
Juice the lemons easily - a great way to exact as much juice from lemons is to microwave the fruits for a few seconds (10 seconds).
Warm the lemon juice - warming the lemon juice helps it incorporate into the egg yolks well.
Egg yolks / Whole eggs - I find that all egg yolks have a higher risk of curdling but the one whole egg does help stabilize it.
Whip eggs and sugar until light and fluffy - If you whip the eggs with sugar until the sugar almost dissolves it prevents the egg from curdling.
Do not let the curd boil - cooking on low will prevent the curd from curdling. If the curd boils, it will give you lemon-flavored scrambled eggs. So no matter how boring - cook on low heat for 10 to 15 mins.
If you find the curd steaming up - take it off the heat for a few seconds this will help stabilize it.
How to know if the curd is done? You can use a thermometer and check until the curd reaches 170 F., But I find the best test is taste. Once the curd is thick and coats the back of a wooden spoon, taste it. It should not have any taste of eggs or cornstarch. If necessary cook for 30 secs more.
Add butter slowly - this will help bring the temperature of the curd down slowly without curdling.
The curd is best stored in a mason or glass jar in the fridge. The presence of eggs in lemon curd makes it a perishable filling so any item that has homemade lemon curd such as cakes and pie needs to be placed in the fridge.
Avoid keeping fruit curd or citrus fillings in metal containers as the lemon can react with the metal.
Egg yolks can react with metal such as aluminum and cause them to become green in color.