1-First Step: Set up your gentle heat Fill the bottom of a double boiler with 1 to 2 inches of water and bring it to a simmer over low heat. You want the water hot, but not roaring. If you do not have a double boiler, set a heatproof glass bowl over a saucepan of simmering water. This keeps the Lemon Curd from burning or picking up a metallic taste from direct heat. Before you start cooking, gather everything you need. Crack the eggs and separate the yolks if you have not already. Zest the lemon, juice the lemons, and cut the butter into 6 pieces so it melts smoothly later.

2-Second Step: Whisk the base In the top part of the double boiler, combine the egg yolks, sugar, lemon zest, lemon juice, and salt. Whisk until the mixture looks smooth and fully mixed. This is where the flavor starts to bloom. Fresh zest gives the curd a bright aroma, while the sugar softens the sharp lemon juice. At this stage, the mixture will look thin and sunny yellow. That is normal. Keep the heat low and steady so the eggs thicken slowly instead of scrambling. If you want a thicker curd, use 2 egg yolks plus 1 whole egg next time.

3-Third Step: Cook until thick and glossy Whisk constantly as the mixture cooks. Do not walk away. This is the part that rewards attention. After about 10 minutes, the curd should thicken to a hollandaise-like texture. If you are using a thermometer, aim for 170 degrees Fahrenheit. Some cooks check for doneness by coating the back of a spoon. If the curd leaves a clean line when you run your finger through it, it is ready. Keep the whisk moving so the eggs do not curdle. If the heat seems too strong, lift the bowl from the steam for a moment, then return it. Slow and steady wins this race.

4-Fourth Step: Add the butter Once the mixture has thickened, remove it from the heat. Whisk in the butter pieces one at a time until fully melted and smooth. The butter gives the curd that silky finish people love so much. It also helps the spread set up nicely as it cools. If the butter seems reluctant to melt, keep whisking gently. Because the mixture is still warm, the butter should blend in easily and turn the curd shiny and rich.

5-Fifth Step: Strain and cool Pour the lemon curd into a jar or bowl. For the smoothest texture, you can strain it through a fine sieve, especially if you want to catch any tiny bits of cooked egg or zest. This is a nice move if you are serving it to guests or using it for a polished dessert filling. Press plastic wrap directly onto the surface of the curd so a skin does not form. Then refrigerate it until chilled and thickened further. The total time is about 1 hour and 15 minutes, including cooling, though the active cooking part is only around 10 minutes.

6-Final Step: Use it when ready After chilling, your Lemon Curd will be spoonable, spreadable, and ready for action. Use it on scones, layer it in cakes, swirl it into yogurt, or spoon it over cheesecake. It keeps in the fridge for up to 10 days, so you can make it ahead and enjoy it all week long.