I’ve kind of made this my own…
1. Wash about 1.2 kg of grapes (preferably not seedless, because there’s pectin in the seeds that will help the jelly to set, then de-bunch them, pulling them off the stalk.
2. You will be left with about 1 kg (and a bit) of grapes. Put them in a large pan. Add 200 ml water for every kg.
3. Boil them for about 20 minutes, with a lid on – there shouldn’t be much leakage of water or else the grapes will dry out.
4. Mash the grapes then pass them through a sieve. You can do it ‘posh’ with jelly muslin, but a fine sieve is fine. Put the sieve over a jug with a pouring spout (so as not to make mess when you pour it back into the pan! Duh!) and cover with a tea-towel or a couple of sheets of kitchen roll. Leave for 10 or so hours.
5. Measure the juice – you should be left with between 900 ml and 1.1 litres. For every litre, add 750 g sugar. You can go up to 1kg sugar if you like it sweet, but less than 1:1.5 won’t set well. Put a plate in the freezer for the set test.
6. Boil the juice with the sugar and keep on a rolling boil for about 10 minutes before you start to do a set test. It will still be very liquid but perfectly fine to set. You don’t want it to burn or go dark. The sugar shouldn’t really caramelise much – so you want to keep an eye on it. Do a set test by taking the plate out of the freezer, dropping a teaspoon of jam liquid onto it and then putting it back in for a couple of minutes. If it’s jam, it’s fine. If it’s too runny, it needs longer. Another way of checking is to use your ladle or stirring spoon. Hold it above the pan and let it drip. Five or six drips will be very liquid, but the final few will be sticky if it’s ready to set.
7. Decant into sterilised glass jars and leave to cool!