try using
var o = wManager.Wow.ObjectManager.ObjectManager.GetNearestWoWGameObject(wManager.Wow.ObjectManager.ObjectManager.GetWoWGameObjectByEntry(XXXX));
wManager.Wow.Helpers.Interact.InteractGameObject(o.GetBaseAddress);
XXXX = item id of the cauldron
you will likely have to make a travel step to get there, once you are beside the cauldron, it will be closest game object
This is what I used to interact with Benedict's chect...its basic, doesnt check if you have done the quest but...it clicks the chest for me!
Give it a shot