Since there's no guides for this party quest at all (not even on Google), I decided to make this guide. Tangyoon's Cooking Class is for players from lvl 60-90, and can be done in a party of not more than 3 people, meaning you can go in solo as well.
Gist of this Party Quest :
You have 5 items to add into a dish which will be shown to you. You have to choose a monster to summon for the dish to kill (lolwhut), which will then cause the monsters to appear on the top of the chopping board for you to kill (another lolwhut).
The monsters will keep spawning for about 3 minutes, during which you can choose to wait for all of them to spawn then kill them all in 1 shot, or keep killing them until they stop spawning and the next selection begins. You have to kill all the monsters on the chopping board before the next wave can be started.
After the 4th selection, some ember monsters will appear at the bottom, which you have to kill all 5 in addition to the monsters on top.
After all 5 waves are done, you will then have to add salt to the mixture, which just requires you to press the button according to the numbers required, which will slowly fill up. Clicking it correctly will give you a WA/MA +10 buff for 20 minutes.
If you chose the right monsters for the dish and added the right amount of salt, your dish is a success and you will summon the God of Cookery, a large pig at the end. If not, your dish is deemed a failure and a Trashcan will be summoned. The God of Cookery has a buff which only allows critical hits to get through, similar to Ani, while the Trashcan has WA/MA cancel.
God of Cookery
If your dish was a success, after killing the God of Cookery, you will get 2 Chef Certificates and some EXP. You only get 1 Chef Certificate if you fail, and the EXP received is approximately halved.
Exchange 3 of these certificates for Tangyoon's Chef Overall, or 5 of them for Tangyoon's Chef Hat. There is a 2-set bonus of +15 to STR/DEX/INT/LUK, +500 HP/MP and +8 WA/MA.
Clearing 3 successful dishes also nets you the medal of A Great Chef.
Recipes and Monsters Required:
Note - If you chose the correct monster, you will get a message saying you should expect great dishes. If not, you will get a message saying the pot smells funny.
Escargot - Chubby Snail, Red Snail, Orange Mushroom, Wine Bottle, Potted Sprout
Chopped Noodles with Mushroom - Blue Mushroom, Chopped Noodles, Mushmom, Bellflower Root, Bubble Fish
Cold Jellyfish - Jellyfish, Cool Jellyfish, Sr. Bellflower Root, Ice Piece, Potted Morning Glory
Fried Pork - Ribbon Pig, Very Fat Pig, Fire Boar, Nependeath, Octopus
Slime Pudding - Slime, Cube Slime, Cherry Bubble Tea, Snowman, Chocolate Syrup
Salt dosage is random everytime.
One round takes approximately 20-22 minutes out of the whole 30 minutes. The experience is nice though, nearly 1 whole level for 1 round at around lvl 7x for my KoC.
That's all there is to this Party Quest.
Also, just a screenshot of a chopping board full of snowmen.