A lot of adventures start with the party being given a treasure map, or being asked to recover a stolen item or a maguffin of some sort.
"Of course, my clients require the finest ingredients. I trust you will have no problem acquiring them." --Head chef of the 'Exquisite Delights' restaurant.
Decadent tastes call for dangerous ingredients. That's how many parties come to hired to collect such items as gelatin from Gelatinous Cubes and clutches of Griffin Eggs.
Simply put, the best food comes from the most dangerous of places.
This, of course, leads to some interesting logistical problems, like how to collect the gelatin without being burned by its acid, or how to bring back that Carrion Crawler before it starts to rot. But that's part of the fun of a food collection scenario.
Even more exciting is the prospect of having them escort a cook to the creature's lair so that it can be prepared on the journey back. Those groups of bandits, goblins, orcs and kobolds can become major complications that can lead to some interesting plans on the parts of the players.
Where does one find such dens of Iron Cookery? typically in larger cities and royal courts that have sizable amounts of nobles and other eccentric and wealthy types.
Sometimes 'underground' eateries open from time to time, moving from location to location in order to keep the clientele extremely exclusive.
Perhaps there are competitions where great chefs face off to show off their skill in the preparation of the rare shrieking ginger root.
In all of the cases someone has to collect the ingredients, who will it be this time?