Scrub oranges clean. Cut them in half and juice them. Cut the peels into narrow strips.
Juice the lemons and add this juice to the orange peels and juice. You should have 725 ml to 1-1/2 litres (5 to 6 cups) combined, of citrus peel and juices.
Put seeds and some of the membranes into a cheese cloth or muslin bag. Add orange mixture and cheese cloth bag into pot, add 6 cups water. Soak overnight if you want, it helps the peel cook faster.
Boil until the peel is completely soft (enough to easily break apart when pressed between 2 fingers). Remove pectin bag and set aside to cool. Add water, 1 cup at a time, if mixture begins to stick. Squeeze pectin from pectin bag; add to fruit and water.
Measure the mixture. Add 1 cup sugar for every cup fruit mixture.
Bring mixture to a boil and continue to boil rapidly until liquid “ribbons” off a stainless spoon and/or wrinkles when a finger is drawn through a spoonful put on a saucer kept in the freezer for this purpose. Remove from the heat while testing.
This can easily take 20 minutes or more but watch carefully. Citrus fruit has a lot of natural pectin, especially in the seeds and pith, and the marmalade will set quite quickly. Err on the side of slightly under-set if you can’t decide.
Add a knob of butter and stir through. A nice touch at this point, stir in 30-45 ml (2-3 Tbsp) of good-ish scotch.
Fill sterilized jars, seal and process. For our altitude, add 10 minutes to processing time. This should produce 6-8 - 240 ml (8 oz) jars of marmalade.
