The different ways of preparing and cooking the fruit each results in a different type of marmalade. Chunky marmalade, for example, is made by cooking the fruit whole and then chopping it. Coarse or thin-cut marmalade depends on how the peel is cut and fine-shred marmalade is made by adding shredded peel to strained citrus juices to produce a clear, jelly like marmalade. You may find it easier to cut the peel after it has been cooked, scooping out the pips into a muslin bag for boiling up when the sugar is added.
This is the traditional recipe for Seville orange marmalade. Coarsely or finely chop the peel according to your preference. To make about 5kg (10lb) marmalade you will need 1.5kg (3lb) Seville oranges, 4tablespoonslemon juice, 3.6litres (6pints) water and 3kg (6lb) granulated sugar or half granulated, half pectin sugar.
Wash the oranges well, then halve them and squeeze the juice and pips into a nylon sieve set over a small howl. Tie the pips and any extra pith and membrane that have come away during squeezing loosely in a piece of muslin as the pips and pith contain valuable pectin. Slice the orange peel thickly or thinly, depending on how you like it.
Put the sliced peel, orange juice, lemon juice, water and muslin bag in a preserving pan; tie the bag to the pan’s handles for easy removal later on. Simmer gently, to extract the pectin, for 1—3 hours, depending on how quickly the contents evaporate. The contents should be reduced by about a half and the peel becomes really soft.
Carefully remove the hot muslin bag from the side of the preserving pan and transfer it to a nylon sieve over the pan. Using the back of a wooden spoon, squeeze the bag well against the sides of the sieve, allowing the pulpy juice to run back into the preserving pan. Discard the remaining contents of the muslin bag. The muslin can be washed and reused.
Add the sugar, stirring until dissolved, then boil the mixture rapidly for about 15 minutes. Remove from the heat and test for a set, reboiling if not set. When the setting point is reached, skim any scum carefully from the surface. Cool for 10-15 minutes, then stir to distribute the peel. Pot and cover as for jams.