Lemon Curd

Before you start

Lemon curd is lemon juice, sugar and eggs cooked gently until thick, then enriched with butter. It is brighter and sharper than lemon pie filling, with a smooth, spoonable texture that sets firmer as it chills. It fills tart shells, goes between cake layers, swirls into whipped cream and turns a plain scone into a treat.

The balance here uses whole eggs for structure plus extra yolks for richness and a deep yellow color. Heat is the critical decision: too high and the eggs scramble into lumps before the curd thickens. Cook it over medium-low heat, stirring constantly with a spatula, until it coats the spatula thickly and reaches about 77°C (170°F). Strain it to remove zest and any stray bits of egg, then whisk in cold butter off the heat for a glossy, velvety finish. Use a stainless steel or enameled pan, since aluminum reacts with the acid and gives a metallic taste.

Ingredients

• 1 tbsp finely grated lemon zest — from about 2 lemons
• 120 ml (½ cup) fresh lemon juice — from 3 to 4 lemons
• 150 g (¾ cup) granulated sugar
• 2 large eggs
• 3 large egg yolks
• Pinch fine salt
• 85 g (6 tbsp) unsalted butter — cold, cut into cubes

Method

1. Rub the lemon zest into the sugar with your fingertips in the saucepan until the sugar is moist and fragrant. This releases the oils for a stronger lemon flavor.
2. Whisk in the eggs, egg yolks and salt until smooth, then whisk in the lemon juice.
3. Set the pan over medium-low heat and stir constantly with the spatula, scraping the bottom and corners. After 6 to 10 minutes the curd will turn opaque and thicken noticeably.
4. Cook until it coats the spatula thickly and a finger drawn across it leaves a clean line, or until it reads 77 to 80°C (170 to 175°F). Do not let it boil.
5. Take the pan off the heat and immediately press the curd through the sieve into a bowl, scraping the underside of the sieve.
6. Whisk in the cold butter a few cubes at a time until melted and glossy. The cold butter also stops the cooking.
7. Press plastic wrap onto the surface or pour the curd into a jar. Cool for 15 minutes, then refrigerate for at least 2 hours, until set.

Tips for success

• If your stove runs hot, cook the curd in a heatproof bowl set over barely simmering water. It takes a little longer but is nearly impossible to scramble.
• Meyer lemons give a softer, floral curd; reduce the sugar to 120 g if you use them.
• For a firmer curd to slice in a tart, bake the filled, blind-baked shell at 150°C (300°F) for 8 to 10 minutes, just until set at the edges.

Substitutions

Eggs and yolks

Use 4 whole eggs and no extra yolks. The curd will be paler and slightly less rich, with a firmer set.

Lemon juice

Lime juice gives a sharper, greener curd; grapefruit or blood orange juice needs 2 tbsp lemon juice added for enough acidity.

Unsalted butter

Refined coconut oil makes a dairy-free curd that sets a little firmer and lacks the buttery flavor.

Variations

Lemon mousse

Fold the chilled curd into 240 ml (1 cup) heavy cream whipped to soft peaks.

Lemon lavender curd

Rub ½ tsp dried culinary lavender into the sugar with the zest; strain it out with the zest.

Troubleshooting

Curd has lumps of cooked egg

The heat was too high or you stopped stirring. Strain it well; next time use medium-low heat or a water bath.

Curd is too thin after chilling

It was not cooked to 77°C (170°F). Return it to low heat and stir until it thickens, then strain and chill again.

Metallic or off taste

An aluminum or unlined copper pan reacted with the lemon juice. Use stainless steel, enamel or a glass bowl over water.

Storage

Refrigerate in a clean, covered jar for up to 1 week. Freeze for up to 3 months and thaw overnight in the refrigerator; stir before using. Do not leave it at room temperature for more than 2 hours.

Safety notes

Cooking the curd to 77°C (170°F) takes it above the 71°C (160°F) recommended for egg dishes. Refrigerate it promptly. Contains egg and milk.