Bata bata cha is an aerobically fermented dark tea from Toyama Prefecture. There is one grower left in the whole country (Hiraki San) who continues to produce this most intriguing tea.
The tea is traditionally served in gorohachi chawan (五郎八茶碗); a beautiful froth is created by whisking the brewed tea with this meoto chasen (夫婦茶 筅).
The following video provides an idea of the concept.