Coarsely grate the pumpkin flesh and apples and together mix thoroughly with the other ingredients in a large pan. Bring the pan to a boil over a low heat, stirring frequently and, following the instructions on the sugar packet, cook at a rapid boil. Then test to see if it sets. If it does not set sufficiently, extend the cooking time by 1 or 2 minutes.
Ladle into thoroughly cleaned jars while still boiling hot.
Tip: An additional way to disinfect the lid before screwing tight is to use a high-proof alcohol, such as rum. Pour off the alcohol if necessary. Tightly screw on the lid after filling and tun the jar upside-down for about 10 minutes.