1.5kg Seville Oranges (these can be frozen if you want to make out of season)
2 Lemons
1.2L Water
3kg Granulated Sugar
Method
Put a side plate in the fridge.
Squeeze the juice from the oranges and lemons and pour the juice into the pressure cooker.
Reserve the pith and pips and place on a piece of muslin. Tie up to make a bag and place in the pressure cooker.
Slice the orange and lemon rinds to your preference and add to the pressure cooker. It’ll shrink a bit while cooking.
Pour in the water.
Seal the cooker and heat to high pressure. Cook for 15 minutes.
Reduce the pressure.
Remove the muslin bag and squeeze all the juice into the cooker and leave the bag to cool.
Transfer everything else to a large jam pot on the stove.
Add the sugar and heat gently, stirring until dissolved.
Increase the heat and bring to the boil.
Boil rapidly until setting point is reached, 120°C.
To test if the jam will set place a teaspoon full of marmalade on a cold plate; if the mixture stays separate when a finger is drawn through the centre, the marmalade will set.
Skim if necessary.
Leave for 15 minutes so that the peel does not rise, then pour into warmed (sterile) jars.