For the orange-pumpkin jam, cut Hokkaido pumpkin in half and remove seeds. Place in oven and bake at 180 °C top and bottom heat for about 35 minutes until soft.
Wash jars and lids, boil and disinfect with rum. Wash the oranges, grate the peel and squeeze the fruit.
Finely puree and weigh the baked pumpkin halves with the orange juice and peels. Add the appropriate amount of jelling sugar, bring to a boil and simmer for about 4 minutes.
Pour orange-pumpkin marmalade into the jars as hot as possible and seal immediately.