bouquet garni of 2 parsley stalks, 2 sprigs of thyme and 1 bay leaf, tied with string
If you have any leftover mushrooms or tomato skins hanging around these can be added to the stock for extra flavour.
Tip everything into a large saucepan with a pinch of salt then cover with 2 litres of water. Bring to the boil, then reduce to a simmer and cook for 3 hours, skimming when needed. Pass through a sieve and use for your intended recipe. Will keep in the fridge for a week and for three months in the freezer.