Here's a quick guide to explain what this new item is for, exactly.

What is this for?
This is an ingredient used to make a new 300 stat food! (The ingredients are much easier to come by, and don't require the typical meat, fish, and veggie of the first 300-stat foods.) There were six new 300-stat food recipes added in 5.4 - one each for Agility, Intellect, Spirit, Strength, Stamina, and Mastery.

How/where to get the recipes?
In order to learn these new cooking recipes, you must first find and learn one of the 6 (BOP) Recipes which drop from an Ancient Guo-Lai Cachewithin the Guo-Lai Halls.

How/where to get the ingredients?
You can gather/trade/purchase the 3 new uncommon ingredients listed below, as they are not BOP nor have a duration. They drop from rare mobs found all around the Vale. However, the other common ingredients are described as "fresh" and have a duration of 2 hours. For your convenience and efficiency, these fresh ingredients are all located within the Vale of Eternal Blossoms for quick pickup! =)

Now... On to the food!

The 2 recipes which use  Aged Balsamic Vinegar:
-Recipe: Farmer's Delight (Spirit)
-- The strawberries are purchased from Merchant Tantan at Setting Sun Garrison for 50s per stack of 5
-- The rice is looted from bags found within Guo-Lai Halls and the mogu tents around the vale
-Recipe: Mango Ice (Mastery)
-- The mangos are purchased from Merchant Tantan at Setting Sun Garrison for 50s per stack of 5

The 2 recipes which use  Aged Mogu'shan Cheese:
-Recipe: Fluffy Silkfeather Omelet (Strength)
-- The eggs are looted from nests in trees around Mistfall Village
-Recipe: Stuffed Lushrooms (Stamina)
-- The lushrooms are looted from the ground around Tu Shen Burial Ground

The 2 recipes which use  Ancient Pandaren Spices:
-Recipe: Seasoned Pomfruit Slices (Agility)
-- The pomfruit are looted from trees or the ground around Mistfall Village
-Recipe: Spiced Blossom Soup (Intellect)
-- The blossom petals are looted from the lily-like flowers on the ground around the Mistfall Village river