Pflaumenmus

Step 1: Heat the oven to 325°F (275°F fan). Toss the halved 4 ⅜ lb damson plums (Zwetschgen) with the 7 oz sugar and 2 tbsp lemon juice in a large, deep roasting tin, then tuck in the 1 cinnamon stick and 3 cloves. Leave for 15 minutes so the sugar starts to draw out the juice.

Step 2: Bake uncovered for 2 hours, stirring every 30 minutes, until the plums have fallen apart and the juice has turned syrupy.

Step 3: Fish out the cinnamon stick and cloves. For a smooth butter, blend briefly with a stick blender; for a rustic one, just mash with a potato masher.

Step 4: Return the tin to the oven for 2–2½ hours more, stirring every 20 minutes and scraping the edges back in, until it is very dark and thick. It is ready when a spoon drawn through it leaves a clear path that does not fill back in, and a spoonful on a cold plate does not weep juice. A common mistake is stopping too soon: a runny Mus has too little sugar to keep and will go mouldy.

Step 5: Spoon it hot into hot, sterilised jars right to the top, seal at once and turn upside down for 5 minutes. Unopened jars keep for a year in a cool, dark cupboard; once open, keep in the fridge and use within 4 weeks.