Pre-heat the oven to 150°C (300°F/Gas 2). Strip the rosemary leaves from their stalks. Reserve the stalks and scatter the leaves onto a baking sheet and put in the oven for 30-40 minutes to dry out. Remove the dried leaves and put to one side.
Put the chopped apples, together with their cores and pips into a Kilner jam pan. Pour in 1.2 Litre (2 pints) of water and add the reserved rosemary stalks. Bring to the boil then simmer gently for 30-40 minutes or until the apples have turned to mush. Then mash them with a potato masher or fork.
Put the pulp into a jelly bag or a muslin-lined sieve and leave to strain overnight. Measure the strained juice and calculate the sugar; for every 600ml (1 pint) of juice use 450g (1lb) of sugar (you should have about 1.2 Litre/2pints of juice).
Put the strained juice, sugar, lemon juice and dried rosemary leaves into a saucepan and heat over a moderate heat, stirring until the sugar has all dissolved. Bring to the boil and cook at a rolling boil for 20 minutes or until the jelly reaches the setting point. Remove the pan from the heat while you test for a set.
Leave to cool for 10 minutes (to ensure the rosemary is distributed evenly). Ladle into warm sterilised jars, cover with waxed paper discs, seal and label. Store in a cool dark place, and refrigerate after opening.
Storage: 9 months
Recipe courtesy of Kilner