Peel, core and slice the apples.
Put the apples in the slow cooker with the lemon juice, vanilla essence, water and apple juice. Cook for 1 hour on high and 2 hours on low (lid on).
Puree the apples using a blender or food mill.
Return the apples to the slow cooker and add the sugar, allspice and cinnamon. Bring to simmering point and stir well. Leave to simmer for about 2-3 hours (lid off) to thicken, stirring occasionally.
Ladle into warm sterilised jars and seal immediately with hot sterile lids. If you want to go down the hot water bath route, the jars need to be processed for 10 minutes after the water has reached boiling point.