• 1 kg (2 lb 4 oz) plums
• 700 g (1 lb 9 oz) sugar
• 1 cinnamon stick
• 50 g (1¾ oz) mustard powder
• 125 ml (4 fl oz/½ cup) cognac

Halve the plums and discard the stones. Put the plum nalves in a large bowl, scatter the sugar over and leave for 12 hours, covered with a tea towel.

Scrape everything into a metal pot and bring slowly to the boil, stirring often. Boil, uncovered, for 10 minutes. Remove from the heat and allow to cool, then cover. After 12 hours, add the cinnamon stick and then boil again uncovered, for 10 minutes. Remove from the heat, allow to cool and leave, covered, for another 12 hours.

Mix the mustard and cognac together in a small bowl, then stir this through the plums. Bring to the boil and simmer, uncovered, for about 15 minutes or until a teaspoonful dropped onto a plate clings, rather than runs, when the plate is tilted. Overcooking will make the mostarda too firm. Bottle while hot into warm sterilised jars. Seal with the lids and turn upside down. Leave to cool before turning upright, creating a vacuum. Store in the pantry until opened, then keep in the fridge.