Add the blackberries and sugar to a mason jar and muddle into a sloppy mess. Use a wooden to spoon or a muddler to make sure the berries are broken up, juicy and mixed well with the sugar.
Pour in the vinegars, put the lid on the jar, and shake until well combined.
Add the basil leaves.
Keep the jar in the fridge, or on the counter, for 1 week, shaking it once every day.
Pour the mixture through a fine sieve, and keep the liquid in a jar, in the refrigerator for up to 3 months.
Recipe by The Patchy Lawn at http://thepatchylawn.com/recipes/from-the-garden/blackberry-shrub-with-basil/