When we first moved into our home in Crystal Palace, we thought the bush outside our bedroom window was a gooseberry, but we soon realised that it’s actually a Jostaberry; this is a tetraploid hybrid between a blackcurrant and two different gooseberries. It has a rich, dark flavour, reminiscent of all its forebears, and it’s lovely when cooked and just sweetened enough to take the edge off its sharp flavour. In the summer of 2012, having put a net over the bush to keep the birds off at the beginning of the year, we took over 4 kilos of fruit off it, and froze it in 250g bags. Some got used for ice cream or frozen yoghurt, then one day, needing to clear some space in the freezer, Nik decided to invent a cordial recipe. It worked first time, producing a delicious, zesty, quite intense cordial that is absolutely gorgeous with sparkling water, really rather naughty with sparkling wine, and positively dangerous as a vodka sea breeze. If you can’t get Jostaberries - and let’s face it, you don’t see them in the shops - try a 50/50 combination of blackcurrants and gooseberries. We also use Jostaberried to make a very fine infused gin

1.5kgs Jostaberries, or 750g each blackcurrants and gooseberries

500g sugar

2 lemons, roughly chopped

1 lime, roughly chopped

2 thumb sized chunks of ginger, peeled and split into two

800mls water

• Put everything except the citrus fruit into a wok or large saucepan and bring slowly to a boil. Simmer for 20 minutes

• Add the citrus fruit and simmer for another 20 minutes. Remove from the heat, and leave the pan, covered, overnight

• Next day, sieve the cordial into a large pot, squishing the fruit pulp in the sieve to get as much juice out of it as you can. Discard the fruit pulp, then bring the juice to a boil, and bubble till it's reduced by a third. Meanwhile, sterilise three screw top wine bottles by putting them into an oven at 160C and leaving for half an hour (remember not to put the lids in as they have plastic coating on the inside!). When they’ve cooled, pour the cordial into them, and keep in the fridge; they'll keep for about three weeks. To drink, put an inch or two in a tall glass, then top up with fizzy water. To jazz up sparkling wine, put a dessertspoonful in the bottom of a wine glass, and top up with fizz. To make a sort of sea breeze, make the fizzy water mix as above, then add a generous glug of vodka and a couple of bashed mint leaves