When we asked Julian Serrano to come up with a dinner-party menu that would feed 10 people for $100, he said, "One hundred dollars a person? No problem." An understandable mistake: Serrano is the chef at Picasso in Las Vegas, a restaurant that draws serious high rollers, like the table of 12 who recently ran up a tab of $4,000. That's $4,000 each. Once Serrano understood what we meant, though, he rose to the challenge. To do so, he looked to the tapas of his native Spain. The Spanish have centuries of practice coaxing big flavors from a few basic ingredients. Some of the ingredients are so ordinary that we forget how good they can be. Take canned tuna,which Serrano rescues from a long-term dysfunctional relationship with mayonnaise and transforms into wonderful pan-fried croquettes. Remember plain white button mushrooms, spurned when woodland exotics came along? Serrano dresses them up with fennel-spiked pork, and suddenly they're turning heads again. As a main course, guests sit down to a simple ragout of chicken, something Serrano could never serve at Picasso, where customers expect deluxe meals to match the deluxe prices. But, as he says, "Food is food. You don't have to have foie gras every day."