Bring Out the Flavor of Ingredients
1) This quest is in Dion in the Temple with Magister Rollant. He wants to make a dessert and needs you to hunt Kadif Werewolves, Giant Mist Leeches, Dire Wolves and purchase 2 Antidotes.
2) The best place to do the Werewolves and Dire Wolves is at the Plains of Dion port because they are both there. The Moonflower quest item drops much faster than the Fruit does , I'd guess that the Moonflower is 1/4 and the Fruit is 1/10. You need 20 Moonflowers and 4 Ritron Fruit.
The Giant Mist Leeches are found around Cruma Swamp, the drop rate is also around 1/4. You need 10. When you have all the items head back to town and remember to pick up the 2 Antidotes from the Grocery Shop.
3) Return to Rollant and he will give you Ritron Jelly after wasting your time by telling you to wait over and over. It's worth a whopping 960 in the store.
I'm not sure if it's random, or it has to be triggered by doing the Grand Feast quest but you can also get his dessert recipe which is needed for that quest as well. If you choose to sell it, it sells for 20,000 at a shop.