All of this really started with one cup of tea? Do you really offer this as a basic translation? This is supposed to be a question, isn't it?
It may not be the "standard" way of phrasing a question in English, but this phrasing is often used.
Should "čaje" be "čajem"? (see http://prirucka.ujc.cas.cz/?slovo=%C4%8Daj)
It should be genitive as shown -- a cup OF tea -- even though šálek is the instrumental.