Prepare the pears – peel, core and cut the pears into decent size chunks and place in a bowl. Pour over lemon juice to prevent browning.
Soften the fruit - empty pears and lemon juice into preserving pan along with 50 mls of water. Cover with a lid. Cook on a gentle heat for 10 to 15 minutes until tender. Shake the pan a couple of times during cooking to prevent fruit sticking to the pan.
Add sugar – remove lid and stir in jam sugar. Keep stirring until sugar is fully dissolved and no visible grains remain. Increase the heat to medium.
Optional: crush some of the pear pieces to give more body to the jam.
Boil to setting point – bring the mixture to a gentle rolling boil and cook for about 10 minutes until it reaches 104°C / 220°F.
Check the set – remove your pan from the heat. Test for setting point by dropping a teaspoon of jam on a chilled saucer. Return to the fridge for 1 minute. Push the jam gently with your fingertip - if it crinkles, (or at least holds the gap your finger makes) it’s ready. If not, reboil for a couple of minutes and repeat until setting point is reached.
Optional - carefully stir in vanilla extract if using.
Pot the jam – let the jam rest for 10 minutes to prevent fruit from floating to the top. Then carefully ladle into warm, sterilised jars, filling to within 10mm to 6mm of the top (⅜” to ¼”). Gently lift and tap the jars on a cushioned work surface to remove air bubbles before sealing tightly.
Store in a cool, dry place out of the sunlight and use within 12 months.