Court-Bouillon

Put the cold water, white wine and vinegar into a wide, non-reactive pot. Add the sliced carrot, onion and leek, the lemon rounds and the salt. Everything goes in cold and together — the acid and aromatics need the full heat-up to leach their flavour into the liquid. Use a stainless or enamelled pot, never bare aluminium, which the acid will dull and discolour.

Tuck in the bouquet garni and the cracked peppercorns and coriander. Bring the pot slowly to a gentle simmer over medium heat, then drop it to the barest tremble and hold for 20-30 minutes. A lazy simmer, not a rolling boil — hard boiling muddies the broth and drives off the delicate aromatics. The kitchen should fill with the smell of herbs, wine and warm lemon.

For poaching whole fish or shellfish, let the broth cool to warm or even cold before the seafood goes in, so the flesh heats gently and stays moist — a violent boil seizes and toughens it. For poaching fillets or as a ready bath, strain the broth through a fine sieve, pressing the aromatics, and discard the solids. Taste and adjust salt and a final squeeze of acid. Use within a day, or freeze.