Classic Lemon Curd

The British have a talent for understatement, and calling this radiant preparation "curd" is a fine example. Lemon curd is not curdled in any meaningful sense—it's a smooth, glossy, intensely flavored cream that happens to involve eggs and citrus cooked together until they thicken into something approaching solid sunshine. The Scandinavians, who adopted the recipe with characteristic enthusiasm for all things citrus during the long dark winters, call it sitronkrem—lemon cream—which is both more accurate and less off-putting to the uninitiated. The technique is a gentle dance with heat. Eggs and lemon juice, left to their own devices over direct flame, will scramble. A double boiler provides the insurance policy: the bowl never gets hotter than boiling water, which isn't hot enough to scramble eggs but is perfectly adequate to thicken them. The butter, added at the end, gives the curd its characteristic silkiness and a slight richness that prevents the lemon from becoming too aggressive. What you do with the finished curd is limited only by imagination. It fills tarts and tops pavlovas. It spreads on scones and mingles with yogurt. It makes French toast transcendent and transforms a simple cake into something memorable. A jar in the refrigerator is a kind of insurance policy against bland desserts.