Martha's red onion chutney

Slice the onions into quarters, then thinly slice.

Heat the olive oil in a large saucepan and add the mustard seeds. Fry for 1-2 minutes until they begin to smell fragrant, then add the onions and chilli to the pan, and cook over a low heat for 20 minutes, until soft and the onions are beginning to caramelise.

Add the sugar and vinegars to the pan. Turn the heat up to medium and simmer for 30 minutes, stirring occasionally, until the chutney is dark in colour and beginning to thicken.

Divide between sterilised jars and seal. Allow to cool completely, then store in a cool, dark place until ready to eat, or label up and give as gifts. The chutney tastes best when it has matured in flavour for around a month, so be patient if you can.