Where I live (in Canada) they tend to use balls of dough in the middle of the pizza to get the same effect, instead of the piece of plastic I've seen elsewhere.
Where in Canada? Turns out it's a pretty big country ;-) I grew up in the Vancouver area and never saw dough balls.
[1] comments like this are a bit of a peeve of mine as they contribute to the global mental picture of Canada as one homogeneous biosphere instead of a huge land mass with many different cultures and environments. Ever heard this one - "Oh, you're from Canada? My brother in law is from Canada; Jake Unrau - ever met him?"
I'ved lived in Toronto and Calgary, never seen any balls of dough (visited out East, no balls that I remember). Always those little plastic things or naught.
