To make the bouquet garni, lay one leek leaf flat on a board, put the herb sprigs and bay leaf on top and cover with the other leek leaf. Tie with kitchen string to secure and use as required.
To make the stock, pour the water into a heavy-bottomed dish or large pot. Add the bouquet garni, celery, carrots, shallots, peppercorns, white wine vinegar, star anise and bay leaves. Add salt and pepper to taste. Bring to the boil, skim off any scum and reduce the heat until the stock is simmering. Leave to simmer for about 40 minutes.
Add the whole trout and – depending on the size of the fish – poach gently for 10-12 minutes, keeping it at a gentle simmer. Take the pot off the heat and allow the fish to cool in the pot before serving.
