Chop but don’t peel about 750 g (½ lb) mixed washed vegetables. Put the vegetables in a pan with 10 black peppercorns, 4 tablespoons lemon juice, 1.2 litres (2 pints) water and a little salt. Bring to the boil, skimming the surface with a large metal spoon, if necessary. Reduce the heat and simmer gently, covered, for 30-45 minutes. Strain through a fine sieve and discard the vegetables. Makes about 900 ml (1½ pints) stock. This can be stored for up to 2 days in the refrigerator.