Hen's Egg
free-range egg · battery egg · Gallus gallus domesticus
The egg is the most nutritionally complete and culinarily versatile ingredient in the kitchen. A single egg contains all the amino acids necessary for life, significant fat-soluble vitamins (D, A, K, E), choline for neural function, and the lecithin in the yolk that makes it the foundation of emulsified sauces from mayonnaise to hollandaise. The white and yolk behave as entirely different ingredients — the white sets at 62–65°C, the yolk at 65–70°C — which is the basis of soft-boiled, poached and slow-cooked eggs.
The white is clean, neutral and very mildly sulphurous when cooked. The yolk is rich, fatty and deeply savoury with a characteristic egg-yolk flavour from sulphurous compounds. Free-range eggs from hens with outdoor access have a slightly richer, more complex yolk flavour.
The white sets at 62–65°C: gels from liquid to a soft, opaque solid. The yolk sets at 65–70°C: transitions from liquid to soft-set to firm. Overcooked eggs become rubbery from protein over-denaturation. The ideal scrambled egg is barely set; the ideal soft-boiled egg has a just-set white and a liquid yolk.
In the UK, refrigerate to extend shelf life. In continental Europe, eggs are often stored at room temperature away from sunlight (the unwashed bloom on UK eggs means refrigeration is preferred). Bring to room temperature 30 minutes before baking for best results. Use within the best-before date.
Crack on a flat surface, not a bowl edge, to avoid shell fragments entering the egg. For poaching: use the freshest eggs available (the white of a fresh egg is denser and coheres better). For hard-boiling: start in cold water, bring to the boil, then immediately cool in ice water to prevent the grey ring forming around the yolk.