Chop the apples including peel and core and place in a large pan with the water, cider vinegar and half the chillies. Bring to the boil then simmer for 25 minutes until the apples are completely soft.
Pour the contents through a muslin cloth or jelly bag suspended over a large bowl. Leave to drip for at least 5 hours — do not squeeze the bag or the jelly will turn cloudy.
Measure the strained juice. Place a small plate in the freezer for the setting test.
Pour the juice into a clean pan, add 450g of sugar per 570ml of juice and heat gently, stirring until the sugar dissolves. Bring to a rolling boil and boil for 10-15 minutes.
Test for setting point using the frozen plate — drop a small amount of jelly on the plate, allow to cool for 30 seconds, then push with your finger. If it wrinkles it is ready. If not, boil for a further 5 minutes and retest.
Remove from heat and allow to cool for 10 minutes then stir in the remaining finely chopped chillies. This helps distribute them throughout the jar rather than having them float to the top.
Pour into sterilised jars, seal immediately and leave to cool completely.
