those 3 things won't taste good by itself. It is really depends on how you cook it.
for carvier, i like it with toro. i had it in a japanese restaurant. they put carvier on toro and it was excellent. (didn't put soy sauce, cause carvier is salty already)
the "traditional" way is to use thin egg to wrap carvier. but i don't like it so much.
Foie Gra. it is just liver. the way to cook it is even more important. the best Foie Gra i had was in Taiwan in a tappen-yaki restaurant. it was a fresh liver, not paste.
truffle has a unique flavor. it is hard to describe it. i like it pair with seafood. it is not good or bad.. it is unique.
there are 2 kinda truffle, winter truffle and summer truffle. they taste very different. summer truffle has a stronger flavor. winter truffle is cheaper.