A friend of mine used to make mushroom-flavored cup a soup and put magic mushrooms in it. That was to improve the flavor. Can this also be done with truffles?
Yes, I have often heard that people did this to mask the taste. It would probably be possible with truffles too, but just like with magic mushrooms, you have to watch out for a few things. Remember that at temperatures above 70 degrees Celsius. psilocybin and especially psilocin oxidize. That means that it then reacts quickly with oxygen and is no longer active.
A suggestion: First, heat the water to boiling point. This allows you to make the soup in whatever flavor you prefer. Only add the crushed or finely chopped mushrooms or truffles after about 5 minutes. Crush or chop them just before adding to prevent reaction with oxygen. Extra tip: If you have truffles in a vacuum bag, you can also crush them in a sealed bag.
Did you know, by the way, that back in the day, before the ban on magic mushrooms, there was also a brand that had ready-made mushroom soup? You could heat this up too, but not too hot. This was the Exquis Mushroom soup.

I think it's a bad idea to enhance the flavor of magic mushrooms and truffles. It is actually good that they aren't that tasty, because that way you think twice about whether you really should do it. And you also take less if it tastes bad.
Yes absolutely, this works great with truffles too! As Marcel already said, make sure you don't heat the soup too much, set the water to about 70 degrees maximum, and only add the truffles just before serving. This protects the active ingredients from oxidation.
It was never this good with soup. I can finish it better with chocolate or a banana. If I had to choose soup, it would be tomato or chicken soup for me; otherwise, you get a mushroom flavor with more mushrooms due to the mushrooms, and that is a bit too much for me.