If you don't get much of an answer here, you could try asking /r/AskCulinary. It may not be the standard kind of fare there, and they won't have the same strict standards in terms of sourcing and all that, but I have seen people there talk about the history of the culinary world in there before.

Just to clarify, your question implies, but does not explicitly state, that you are interested in food preparation-type jobs. Are you asking about those types of jobs only, or any jobs in a Medieval aristocratic household?