Squeeze the lemon juice into a bowl.
Peel and core the pears, then chop them into small pieces and put them straight into the juice bowl.
Tip the pears and juice into a suitable pan and add five teaspoons of water.
Put on a medium-low heat and cook, stirring, for five minutes.
Add the sugar, vanilla extract and cinnamon, and simmer, stirring pretty constantly, until the sugar dissolves.
Bring to a boil, stirring often to prevent scorching, until the jam reaches setting point – test this either by temperature (104C) or with the wrinkle test on a cold plate.
Stir in the chocolate, making sure it is completely melted and well distributed through the jam.
Ladle into hot, sterilised jars, quickly seal with their lids, then invert and leave them lid down until completely cool – this will help create a better seal.
The jam will now keep in a cool, dark cupboard for up to a year. Once opened, store in the fridge and use within a month.
