How to Make It
In a mortar, lightly crush the peppercorns with the allspice, juniper berries, ginger and bay leaf. Transfer to a medium saucepan and add the vinegar, water, sugar, salt, shallot and thyme. Bring just to a boil, stirring to dissolve the sugar and salt. Let the brine cool completely.
Strain the brine into clean glass jars and add the blackberries. Cover and refrigerate for at least 1 week before serving.