Which Kundera novel is this in?

There is a hilarious scene in one of Milan Kundera’s novels about two friends who sometimes sleep with the same women. As a practical joke, one of them teaches a woman to say excruciatingly dirty things while she is having an orgasm with the intention of his friend hearing it. Later, the friend does indeed hear the women saying these things at the height of passion and he feels his friend standing over his shoulder laughing at him. The interesting point is that Kundera discusses human sexuality as a pool of rituals and techniques that are passed on from person to person.

I wish to quote from this story, but I can’t seem to find it. I believe it is in either: Immortality, Slowness, or Identity. I’m fairly certain it is NOT in Unbearable Lightness of Being.

If you can find the page number of the book it’s in, that would be even better. :)