- Heat the oil in a large heavy-based saucepan or stockpot. Add the leeks and onion, stir well and reduce the heat to low. Cover with a tight-fitting lid and leave the vegetables to sweat for about 20 minutes, shaking the pan occasionally but without lifting the lid.
- Add the bay leaf, thyme, parsley, carrots, celery and salt. Pour in 2 litres (3 ½ pints) cold water and increase the heat to high. Bring slowly to the boil, skimming the surface of the liquid to remove any scum.
- As soon as the water boils and all the scum has been removed, add the peppercorns and reduce the heat to low. Cover and simmer for 35 minutes.
- Strain the stock into a large, heatproof bowl and set it aside to cool. Use at once or cool and then chill until required.
Because this stock is mild and has a light flavour, it works well when used as a cooking liquid for rice and pasta and adds useful nutrients to the meal.
Home-made stocks, such as this one, contain some calories (approximately 33 kcal per pint) and a small amount of fat (3–4 g per 500 ml/1 pint), but also contribute beneficial nutrients.