Sweet orange jam

Instructions

1. Place the oranges in a large bowl or bucket and cover with water. Cover with a clean tea towel and place in a room that is not heated. Change the water every 12 hours for 3 days. On the fourth day, drain the oranges and remove the rind at the ends of the oranges. Cut each orange in half lengthways, then cut into segments no more than 5mm (¼ in) thick (you can cut them thinner or into pieces if you do not like chunky jam). Weigh the oranges (I still had 1.5 kg/3 lb 5 oz as they had absorbed some water) and place in a large saucepan that will easily fit them all. Add the same weight of water (in my case, 1.5 litres/52 fl oz) and the lemon juice, then bring to the boil and allow to boil for 10 minutes. Weigh out the same amount of sugar as you had sliced oranges and add this to the pan – it should dissolve fairly quickly. Bring to the boil, then reduce the heat so the orange mixture bubbles away gently.
2. Check every 15 minutes or so, giving the mixture a good stir. After about 1¾ hours the syrup will start to reduce and thicken.
3. Meanwhile, preheat the oven to 110°C (225°F). Wash some lidded glass jars so they are completely clean, then place them in the oven with their lids upturned to sterilise them. Turn the oven off after about 30 minutes and leave them there until needed. I also sterilise a 500 ml (17 fl oz/2 cup) heatproof glass jug at this point, as I will need it later to help me pour the jam into jars.
4. Place a small plate in the freezer.
5. When the jam mixture has reduced and the syrup is looking thicker, test it for readiness. Place a small teaspoon of jam on the chilled plate. If it sets and is not too runny, it is ready. If it is still runny, return the plate to the freezer and cook the jam mixture for another 5-10 minutes before testing again.
6. When the jam is ready, remove it from the heat and stir in the rum. Remove the jars from the oven and pour the jam directly into them (or use the sterilised jug to fill the jars) to about 5 mm (¼ in) from the top. Secure the jars with the sterilised lids, them turn them upside-down. Set aside until the next day, then turn them the right way up. This should form a seal, allowing you to keep the jam for up to a year. Once opened, store it in the fridge.