This a recipe that I have used for a number of years. It's quick and can be done over two days, so you can fit it around other jobs.
I buy a years’ supply of Seville oranges and put them in 2lb lots into freezer bags and freeze them so that I can make batches of marmalade throughout the year.
I have never failed with this recipe. I hope it works for you!
2lb Seville Oranges
4 pints of water
4lb of sugar (cane sugar)
Cut oranges into eighths and take out pips. Cut pith out of lemon and finely cut peel. Put the oranges in batches into a food processor with a little of the water and blend until you get the size of chopped peel of your choice.
Put the oranges and the lemon into a preserving pan add the rest of the water, place the pips and pith from the lemon in a piece of muslin, tie and lower into the pan with the fruit. Bring to the boil. Then turn heat to low to a slow rolling simmer and leave for 1 hour, stirring occasionally.
Add the sugar and carefully stir every now and then,making sure the sugar is fully dissolved, turn up the heat until the marmalade reaches boiling point . Keep a rolling boil until it reaches jam temperature on a cooking thermometer or the marmalade sharply flakes off of a wooden spoon. A saucer cold from the fridge with a small amount of marmalade on it will also show the amount of set.
A knob of butter in the marmalade will dissolve any scum, you are then ready to carefully put it into jars. I sterilise my jars in the micro wave, just pour water in about a quarter way up and bring to boiling point. If I’m busy I sometimes leave putting in the sugar etc until the next day.