Boukensha Sakaba no Ryourinin

Yoishi, the bar owner, feels sorry for the poor food that adventurers eat. One day, he begins to search for a way to cook the bitter and inedible "stone walnuts" that can be found in the labyrinth of the city for a group of rookie adventurers...? A chef and a variety of labyrinth ingredients dramatically change the humble food situation in another world in this thrilling tale of a successful bar!!

(Source: Comic-Walker, translated)