Prepare a 500ml pickling jar by washing the jar and lid, removing the rubber seal. Place in the oven and heat at 100ºC/gas ¼ for about 30 minutes. Immerse the rubber seal in a pan of boiling water and simmer for about 10 minutes before turning off the heat and allowing to cool.
Peel and finely slice the shallots, then destone and roughly chop the plums. Heat the vegetable oil in a pan that’s big enough to hold all the ingredients. Add the shallots and cook gently over a low heat until softened and golden-brown. Add the bay leaves and spices, fry for a minute, then stir in the plums. Add the sugar and grate in the orange zest.
Squeeze the orange juice into a measuring jug and top up to the 450ml mark with cider vinegar. Add to the pan and bring to the boil, then simmer slowly until most of the water has evaporated and the chutney is reduced and thick, stirring now and then as it cooks.
Pat the jar seal dry with kitchen paper, fit it back onto the lid and have the jar standing by. Spoon the chutney into the sterilised jar while everything’s still nice and hot. Wipe the rim of the jar and seal it. Leave to cool and store in a cupboard for a few weeks before eating.