In the last level of the cave, there is a green goblin girl, let her fuck you and she will give you the recipe.
Relax friend, it's fun to progress with other people and help in whatever way possible, as for volupta I suppose it's for the next update, I also took the medallion and looked for her everywhere, but I couldn't find it, I read it on different forums and websites ( that's how I found the answer to the recipe) and even then I didn't find anything about the volupta, I just got a boobjob scene using the codes from benbo's little house.