Chop the cucumber into a few chunks,
then put in a blender or food processor
with the wine and elderflower cordial.
Whizz until well blended, then pour
through a sieve set over a large bowl or
jug. Tip the contents of the sieve back
into the machine, whizz again until pulpy,
then sieve again into the liquid already
collected. Add 1-2 tbsp of the cucumber
pulp from the sieve into the liquid and
discard the rest. Chill until ready to serve.
To serve, fill glasses with a few ice
cubes and some mint leaves. Pour in
enough cucumber base to come halfway
up the glass, then top up with soda water.