Boil the whole oranges in 2 litres water until very soft – it will
take about 2 hrs. Pour the liquid into
a preserving pan or a large saucepan.
Cut the oranges into wedges, flick
out the pips with the point of a knife
then gently squeeze the wedges over
the pan as they’ll be very juicy. Thinly
slice them, then add to the pan with jam sugar. Dissolve over the
heat then boil for 7-10 mins, stirring
occasionally, until a little of the mixture
dropped onto a chilled plate sets and
wrinkles when you push your finger
through. Leave to settle for 15 mins
before potting into sterilised jars.