well France was only a small nation in the past as what we now know as France were indeed separate kingdoms burgundy Alsace Brittany Normandy the basque region were all country,s in their own right . so you see France is only a young country . so as far as food is concerned the peasants ate a gruel type of porridge whilst the upper class ate on fine meats and game and when France was united by marriage or by conquest this remained the same . if a peasant were to be caught eating meat or game then they would be put to death for stealing the kings food .
that’s what started the revolution and caused the downfall of the french monarchy.
and as chefs worked for the dukes counts etc they were now out of work and thus the restaurant trade started up i could go into more detail but i think that it would be better for you to try and do some research as i do think that you would gain much more in doing that