Method

• Put the grapes and apple in a large pot and add 1/2 cup of water
• Bring to a boil, cover and simmer over low heat until very juicy, about 10 minutes
• Strain the juice through a fine sieve set over a large bowl
• Strain the juice again through several layers of dampened cheesecloth, without pressing or squeezing; you should have 3 cups – I usually do this overnight
• In a very large saucepan, boil the grape juice and sugar over moderate heat, stirring, until the jelly thickens
• I place a small spoonful of jelly onto a cold saucer and place somewhere to cool
• If it stays apart when you run your finger through it then it is ready or if you have an instant-read thermometer and it registers 220° about 18 minutes
• Pour the jelly into hot, sterilized jars to within 1 cm of the rims
• Seal
• Submerge the jars in a pot of water and boil for 5 minutes
• Carefully remove the jars and let cool
• Check the jar lids to make sure they’ve fully sealed; refrigerate any jars with imperfect seals