Make a pickling vinegar by heating – in a Bain Marie – all your favourite spices with one spoon of soft brown sugar and a pinch of salt per cup of cider vinegar. Infuse for 5 minutes then leave to cool. Strain it before using it.
Ideas for spices include: peppercorns, ginger, cinnamon, chillies, cloves, bay leaf, coriander seed… Or use wild spices like hogweed seed, ground elder seed, wild leek seed… See my wild spice chart here.
Pick the ash keys when they are really, really young and green. As early as possible or they get stringy.
Put the ash keys into boiling water and simmer for 5 minutes. Remove and change water. Simmer in new water for 5 minutes. Strain. Cool a little.
Pack the cooled keys into preserving jars leaving a 3 cm (an inch) of space at the top. Fill with your spiced vinegar right to the top.
Seal. Leave for 3 months. Eat!