1. Place chopped carrots, celery, onion and a bouquet farni into a large stockpot. cover with water and bring to the boil. Reduce the heat and simmer the stock for up to 1 hour.
2. Ladle through a fine sieve, pressing the vegetables against the sieve to extract any extra liquid. Season to taste with salt and freshly ground balck pepper, let cool and refrigetate for up to 3 days.