Ambrosias are used in the Test of Festivals as a sacrifice to the gods.
How to make
Once you select Ambrosia, you will get a selection window where you will have to select a simple and a complex ingredient (both of them in the same selection window), and a label where you can enter the name of this ambrosia (Common names are, for instance, "<God> - <player>" or "<God> - <complex attribute>")
Once you have filled in the name and selected the 2 ingredients, the cooking process will start and last 10 minutes.
This is longer than the 10-minute cooking time in previous tales.
Tale 7, Year 3, Shemu IV-7 my popup said 10 minutes for Isis Ambrosia, and was ready for collection after 11 minutes -- Silden 01:19, 16 October 2016 (EST)
Do note though : While you get a pop-up saying the process starts, you don't get a message in Main saying the cooking started, nor does the kitchen look to be working. But the process is actually underway, and after 10 mins you can take the ambrosia from the kitchen.