• 150 g (5½ oz) jamón, cut into large dice
• 1 stalk celery, chopped
• 1 carrot, chopped
• 1 onion, chopped
• 1 head garlic, halved widthways
• 1 fresh bay leaf
• 2 sprigs thyme

Place all the ingredients in a saucepan. Add 1.2 litres (42 fl oz) water and bring to the boil, then reduce the heat to 85°C (185°F) and simmer for 2 hours, keeping the stock at 85°C and skimming the scum from the surface regularly. Strain, discarding the solids.