Tirami sù is actually a contemporary revision
of a traditional Italian dessert called zuppa inglese (English
soup), named because English artists living in Florence were particularly
fond of it. Zuppa inglese contains ingredients similar to
tirami sù , substituting custard for the mascarpone.
The Dictionary of Italian Food and Drink credits the El Toulà
restaurant in Treviso with originating the dessert in the 1960s.
It took a while for its fame to spread, but in the 1980s it became
a popular menu item in San Francisco's North Beach Italian restaurants
and has now become a staple at Italian restaurants everywhere.
What does tirami sù taste like? Let me
quote from Craig Miyamoto, who describes himself as a "self-styled,
self-proclaimed, semi-professional tirami sù gourmet"
on the aforementioned tirami sú web site he created and
maintains:
"Imagine that you're dressed in gossamer. You
have delicate white wings and are sitting on a fluffy cloud. You
are experiencing the greatest dessert ecstasy of your life. You
are in Heaven, and Heaven is in your mouth."