From Fern Verrow: Recipes from a Biodynamic Farm by Jane Scotter and Harry Astley.
Raspberry vinegar
Makes 6 x 250ml bottles
1kg berries
600ml cider vinegar
granulated sugar
Always use the freshest fruit you can get hold of, but remember it doesn’t matter what the fruit looks like, as you’re going to mash it up for its juice. It is important that the fruit is dry, especially if you are using strawberries and raspberries, so try not to wash it. You can also use a mixture of elderberries and wild blackberries for a foraged, more savoury vinegar.
1 Put the berries into a large ceramic or glass bowl. Add the vinegar and gently crush the fruit with a potato masher or a large fork. Cover tightly and leave in a cool room for at least 5 days, stirring once each day.
2 Line a sieve with a piece of sterilised muslin, set it over a bowl and pour the fruit and vinegar into it. Tie the corners of the muslin together and suspend the bag over the bowl for 12 hours for the juice to drip through.
3 Measure the juice and allow 450g sugar for every 500ml. Put the juice and sugar into a large stainless steel saucepan, place over a low heat and slowly bring to the boil, stirring until the sugar is completely dissolved. Boil for 10 minutes, then remove from the heat and leave to cool. Pour into sterilised bottles and seal straightaway. It should keep for at least a year.