Many cities have their own "signature" version of pizza, and proponents of each type of pizza are willing to argue all night that theirs is the best - whether it be from the source in Naples; or a large, thin New York slice; or perhaps a hearty deep dish from Chicago. Here in Los Angeles, we don't really have a "signature" pizza, except perhaps the use of untraditional toppings, made famous by Wolfgang Puck. But even so, you can get a "California-style" pizza at five different places and have five completely different pizzas even in the most definitive aspects, like crust thickness and cheese-to-sauce ratio. It would be a fine thing if we decided to make Nancy Silverton's style of pizza the definitive Los Angeles pizza. In my book, it can compete with any pizza anywhere. It's not just the variety of really good, really fresh ingredients in both unusual and familiar combinations. It is mostly the crust. A crust that was carefully created through