I found this recipe in the book 'A Year on the Farm' by Sally Wise. It is very simple to make, but I have slightly changed the method over time.
Quantity: 11/4 litres
Author: sbaskitchen
Ingredients
1kgblood oranges
1litre good quality white vinegar
Sugar
Instructions
Use a food processor to mince the whole oranges.
Place them in a large jar and add the vinegar. Stir to mix well
Put the lid on the jar and leave it to stand at room temperature for one week.
Use a strainer to separate the solids from the liquid. Dispose of the solids and retain the liquid.
Using four thicknesses of muslin, strain the liquid again.
Measure the liquid into a large pan, and for each 500 ml of liquid add 175g of sugar.
Bring to the boil, stirring until the sugar dissolves.
Leave to stand for 5 minutes and then, using a flat spoon, skim off any scum.
Pour into sterilized bottles and seal immediately.
Leave for at least a month before using.
Notes
While the original recipe does not include all of these steps, I have added them to ensure a beautiful clear finished product. If you do not wish to follow this the vinegar will have sediment that does not change the flavour, but just doesn't look as pretty.
I repeat step 5 twice!
I've halved the amount of sugar used in the original recipe.