Jean-Pierre is Mallory's chef de cuisine, which is a term for the head or executive chef. He's physically described as "darkly handsome" (6.22) when we're first introduced to him; we don't often hear him speak, but instead mostly hear Mallory barking orders at him. Which tells us that he has a decent tolerance level. Usually he reacts by scowling or banging pots and pans around.
He has a jealous streak—a serious one—that flares up when Hassan comes to town. His thirty-seconds of fame happens when he throws a tantrum toward the end of Chapter 12, getting super mad and throwing stuff because Mallory gives Hassan more attention. Mallory rewards his years of service by adding to her will that he will inherit Le Saule Pleureur after she is dead. Not too shabby, if you ask us. Our temper tantrums haven't paid off nearly so well.