discourse on

discourse (up)on

someone or something to lecture about someone or something. (Upon is formal and less commonly used than on.) I would like to discourse upon this matter awhile. The committee chose to discourse on Tom and his latest fiasco rather than deal with the budgetary problems it faces.
See also: on
References in classic literature ?
The Frenchman left them for friends at another table, and Cronshaw, with the lazy enunciation which was one of his peculiarities, began to discourse on the relative merits of Kent and Lancashire.