manipulating chapter title page in html

I just can't seem to find the right place to manage this. I want to remove the "Chapter 13." part of the title of this pattern:  "Chapter 13. My Chapter Title", which is generated in the main entrypoint (toc file).

I traced through user.head.content which stops just before the title, and found make.toc which seems to start just after the title.
My guess is that is comes from chapter.titlepage.recto.auto.mode which calls chapter.titlepage.recto.mode but then I get lost.

thanks for any pointer to the correct template!
--Tim Arnold