Plum membrillo with cinnamon and sage

Method

1. Wash the plums well, then halve, stone and put in a heavy-based pan (with a lid) with 500ml water and the cinnamon. Put the pan over a medium heat and bring to a simmer. Cover the pan with the lid and cook for 20 minutes until the plums are very soft.
2. Let the purée cool a little, remove the cinnamon, then press it through a sieve into a bowl using a wooden spoon (discard any solids). Return the purée to the washed pan.
3. Put the pan back on a low-medium heat, bring up to a simmer and bubble gently to reduce the purée by half (about 25 minutes). Stir in the sugar and cook over a low heat, stirring constantly, until the sugar has dissolved. Turn up the heat and cook until the mixture becomes very thick (30-45 minutes). Be careful: the bubbles are somewhat volcanic and can spit burning hot jam. I find it’s best to use a flat-edged wooden spatula to stir and scrape the pan, which you’ll need to do every minute to prevent the mixture catching and burning on the base of the pan.
4. The plum membrillo is ready when the spatula leaves a clear line when you scrape it across the bottom of the pan. Add the finely shredded sage leaves and mix in. Pour into the prepared loaf tin and leave at room temperature to cool and set. Cut into 8 equal size blocks and wrap in cling film to store.