At this stage the most important thing is that the nut's interiors are wood-free. After 'topping & tailing', piercing several times with a fine stainless blade, and removing any blemishes, the nuts are washed and put to soak in a brine made from a ratio of 500 gms salt to 6 litres water. They need to soak for between 10 to 12 days, with the brine being changed at least twice.
When their time is up, they're washed and drained, and put out into the sunshine for a couple of days until they turn black. Then they are placed in sterilised jars and covered with a hot sweet boiled spiced vinegar, made from 1lb brown sugar, 3 pts malt (or red wine) vinegar, 1 tsp salt, a few peppercorns, and some cloves.
Leave for at least 2/3 months before tasting; I leave mine till Christmas (I always have plenty in reserve from last year).
Now all that remains is to try to get the brown stains off my fingers. I was going to buy some rubber gloves, but as usual.......