Many years ago someone I worked with who was a German speaker (possibly Swiss or Austrian rather than German) told me there was an expression for what I think he described as a "breakfast engineer" (could have been "breakfast scientist" or something similar - he was a biochemist). The story he told was that it was used to describe people in the later years of their career, whose main quality was experience, rather than up-to-the minute knowledge. Younger colleagues would go to breakfast with them in order to get the benefit of their experience when they had a particularly difficult problem to solve. Does this ring any bells with any German speakers here ? (Needless to say I've Googled this expression and many variations without any success.)
I have never heard the words *Frühstücksingenieur or *Frühstückswissenschaftler. I guess, the word you are most probably looking for is Frühstücksdirektor. Wikipedia says:
Als Frühstücksdirektor wird umgangssprachlich eine hochrangige Führungskraft bezeichnet, die in einem Unternehmen oder einer Organisation keine operativen Funktionen innehat oder diese nicht wahrnimmt.
which can be translated as:
A Frühstücksdirektor is a high rank manager who does not have any operational function in the company or organisation.
Often, a Frühstücksdirektor is hired as a representative, a figurehead. However, the word is also used to describe persons who just have a position in the company due to nepotism. Usually, the term Frühstücksdirektor is used as an insult, suggesting someone with a fancy job title and position is not doing anything.
The only word with a similar sound is "Frühstücksdirektor" (see jonathan.scholbach's answer). But this has a negative connotation whereas your description does not imply that. On the contrary, you say the phrase was used to describe people in the later years of their career, whose main quality was experience, rather than up-to-the minute knowledge. Younger colleagues would go to breakfast with them in order to get the benefit of their experience when they had a particularly difficult problem to solve. There is nothing negative in it, and therefore I conjecture that "Frühstücksingenieur" (or something like that) was either an adhoc invention of the person you worked with or belongs to some sort of company jargon which may be cryptic for external parties.
It may also refer to "breakfast-with-an-engineer events". See for example here and here. Such events are organized for university (or high school) students to get an inside view into the occupational profile of an engineer and into interesting projects engineers work on. I could imagine that some companies adopted this as a sort of regular communication platform for newbies and old hands. In that case a "breakfast engineer" would be an proficient engineer participating in such an event. Anyway, the concept is most likely not of German origin. If the person you worked with used a German word like "Frühstücksingenieur", I would guess that it is just a literal translation.