British Lemon Curd

In a medium heatproof bowl — glass or stainless steel, not aluminium, which reacts with citrus — combine the strained lemon juice, caster sugar, egg yolks, and lemon zest. Whisk vigorously for about 90 seconds until the mixture is uniformly combined and the sugar has begun to dissolve. You will notice the yolks thicken slightly just from the acid and sugar — this is safe at room temperature for the short time it takes to prepare your bain-marie. Do not add the butter yet; it goes in later at a lower temperature to create the emulsion that gives curd its characteristic silky body. Make sure there are no yolk streaks remaining — the mixture should be a uniform, bright canary yellow.

Set the bowl over a pot of barely simmering water — the bottom of the bowl must not touch the water, and the water must not boil aggressively. This bain-marie setup is non-negotiable: direct heat will scramble the yolks before they can emulsify. Cook the curd, stirring constantly with a silicone spatula or wooden spoon, reaching into every corner of the bowl. Do not let the curd sit still for even 10 seconds — the edges and bottom will cook faster than the center. Maintain a constant, gentle motion. After 8–12 minutes the curd will thicken noticeably, shifting from thin and liquid to something that holds a trail when you drag the spatula across the surface. The curd is done when it coats the back of a spoon thickly and a finger drawn across leaves a clean, defined line that does not fill in. Target temperature: 75–82°C (167–180°F). Pull it off the moment it nappe-coats the spoon — the residual heat continues cooking.

Remove the bowl from the heat and immediately pass the hot curd through a fine-mesh sieve into a clean bowl — this catches any chalazae (white threads) or cooked egg bits and ensures a perfectly smooth curd. Add the cold, cubed butter to the sieved curd all at once. The temperature difference is intentional: the cold butter cools the curd rapidly (stopping the cooking) while simultaneously emulsifying into it. Stir gently with the spatula, encouraging each cube to melt and incorporate. Add the pinch of sea salt — it is remarkable what it does to the lemon flavour, lifting it from sweet-sour into something more complex and alive. Once all butter is incorporated and the curd is glossy and smooth, pour immediately into sterilised jars and seal. It will continue to thicken as it cools. Refrigerate for up to four weeks.