After the sugar has dissolved, cool a small portion of the jam and taste. Additional ground black pepper can be added at this stage if required.
For added safety use a splash guard at the boiling and stirring stages.
To sterilise glass jars: Wash jars in clean soapy water and rinse well. Place in an oven on a baking tray at 140 C for 20 minutes. Remove jars with care and allow to cool for 10 minutes before adding the jam. Handle jars with care - they may still be hot.
My plums are really juicy so I didn't use water or butter and boiled it a bit longer. Delicious ❣️ - 07 Aug 2017