Peel two large cukes (or don't if you want an attractive green colour to the vodka for cocktails). Slice in half and remove the seeds. Chop into 1 inch chunks and fill a large clean jar. Cover with vodka and leave in a dark cupboard for five days. Strain with a coffee filter and bottle.
For cocktails, you could just add it it to Pimm's, however I'm experimenting with lychee and rose martinis. Or just on its own, from the freezer.