Place 450g of raspberries in a stainless steel or glass bowl and crush lightly with a fork or potato masher. Pour over 450ml of white wine vinegar, stir then cover and set aside for at least 2 days. Give the fruit an occasional stir. Drain the fruit through muslin and leave for 2 or 3 hours – longer if you have time. Pour the liquid into a stainless steel saucepan and tip in 80g of sugar. Bring to the boil, then lower the heat and simmer for about 10 minutes, scraping off any foam. Leave to cool, pour into sterilised bottles and store in a cool dark place. It will last for a year.
