Method
Give the blackcurrants a quick wash and remove their stalks, as usual, but don’t worry about the papery little base if they have it. Place the blackcurrants, sugar, thyme (if using) and 500ml (17fl oz) water into a heavy-based large pan and place over a low heat, stirring continuously for about 5 minutes, until the sugar has completely dissolved.
Turn up the heat and bring the liquid to a simmer, uncovered, for 8–10 minutes, until the blackcurrants are soft to bursting, then add the lemon juice and zest and remove from the heat to cool in the pan.
Line a sieve with muslin cloth, or use a jelly bag, and place it over a jug or bowl. Pass the cooled fruit mixture through the lined sieve or the jelly bag, allowing it to drain into the bowl or jug for at least 1 hour (2 hours would be better). Encourage as much juice through as possible by pressing the pulp with the back of a spoon every now and then.
Pour the cordial from the bowl or jug into sterilized glass bottles (you can sterilize them by running through your dishwasher on its highest setting), seal the tops, and refrigerate. The cordial will keep for 3–4 weeks.
To serve, place a few ice cubes in a glass, pour over a little of the cordial, and top up with still or fizzy water to taste.
