kitniyot question

I understand from comments on this site that kitniyot is ‘batel berov.’ My question is does that apply to 'bathchila" (in the beginning i.e. knowingly when preparing the dish) or only ‘bedieved’ (after the fact)?

Hope my question is clear with the spelling etc.

Thank you.

You should not mix it in deliberately to be mevatel it.

A manufacturer, for example, is following a specific recipe. His intentions are not to be mevatel an issur.