First, you need to have level 2 cooking skill. Cook few other items to gain more xp.
Now Talk to Lazuli, She’ll Say talk to Dovedel (Drunken Man)
He’ll give you another mission called “Locate the giant Spider and retrieve one of its legs”
Then you go here
Dawn spider den. Over there fight the biggest spider looks like this called “Giant Cave Spider”
That spider drops this two items
Now go talk to Dovedel, he’ll give you the recipe and x3 plump spider leg dish
Give that to Lazuli, She’s happy
Bingo!!! Mission completed