After speaking to the herbalist in Work in Oraport, he will need two items. You need to cook a Red Sea Angelfish and find a barnacle.
The barnacle is by far the hardest of these two. If you read A Blacksmith's Shipment quest guide and learned how to get to pirates bay, finding the ship with the barnacle should not be too hard. Near the coast, keep walking untill you see a palm tree, from there, walk into the water. After a while you should see a shit with a barnacle, right click the barnacle and leave go back
For the Angelfish, the easiest way is to just buy the fish (Trust me just do it). Then around town you should see these iron trapdoors with fire underneath (The best one is the one in the Inn). There you can use it to cook the angelfish (The progress will be on top of the exp bar).
Once you do those things, you can talk to the herbalist again to get your reward.