This time around I tried Nigella's Pink-Grapefruit Marmalade from How to Be a Domestic Goddess. It seems too simple at first glance, but works brilliantly.
You boil two grapefruit for 2 hours, until they're soft. Then drain and slice thinly, chopping a bit (removing any large pips), before returning to the pan, along with 1kg preserving sugar, and the juice of 2 lemons. After boiling for 15 minutes or so, test for setting point. The easy way to do this is to have a plate in the fridge. Place a teaspoon of the mixture on the plate, and leave for a minute. If the surface of the mixture creases when you push it, the marmalade is ready. Pour into clean jars, and seal.
'Foolproof' is a dangerous term, as all recipes require a certain degree of common sense and judgment. My husband points out that often these foolproof recipes are anything but, requiring a considerable level of culinary know-how. For instance, would everyone know what Nigella means by 'boil until setting point is reached'? If you know the jam basics, though, this is a hit.
A couple of notes.
- Nigella doesn't tell you to skim the mixture as it boils. I would recommend doing this though, as the scum that rises to the surface can make the finished marmalade cloudy rather than clear.
- It may well take longer than 15 minutes to reach setting point. Mine took 35 minutes. Be patient, and test it every 5 minutes or so.