In this recipe, matcha tea's earthy, grassy flavor is complemented by celery and aged rum. St. Germain, an elderflower liqueur, adds brightness, while cucumber covers two bases: the peel is bitter and vegetal, whereas the interior is aromatic and melon-like.
If you don't own a juicer to extract juice from celery, you can muddle a few short pieces in with the cucumber. Be sure to crush these pieces thoroughly to extract as much flavor as possible.