Rinse the redcurrants in water, place in a stainless steel saucepan and add the water. Bring to the boil, cover and simmer for 10 minutes.
Mash the redcurrants against the side of the pan. Pour the pulp and liquid into a cheesecloth and leave to strain for 30 minutes.
Return the liquid to the pan. Add the sugar and simmer for 10 minutes. Remove from the heat and carefully skim off the scum.
Dissolve the vanilla sugar and sodium benzoate in a little of the liquid, and stir back into the pan.
Pour the redcurrant squash into warm, sterilised bottles. Seal and store in a cool place.
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