Step 1

Talk to Turpeco in Morroc just south of the inn.
Give Turpeco 50 Jellopy

Step 2

Turpeco asks for the “competition to be thinned out”
Kill 30 Peco Pecos
Return to Turpeco

Step 3
Inside the inn, talk to Chef Oda
Step outside, Talk to Turpeco and select “it's a cookbook!”

Step 4

Back inside the inn, speak to Chef Oda.
A list of different food stuffs will appear, one of which is the correct one.
5 of each are required and all are consumed until the correct foodstuff is selected.
Not all options need to be chosen for the correct one to appear

Collect reward from Turpeco.