First the chefs at AVA, one of whom worked at the Green Room, brought back that long-lost restaurant's mussels recipe. Then the man himself announced his return. Years ago Marc Cassel guided the little Deep Ellum bar/restaurant to greatness. His style? Collision cuisine—the happy smashing of contrasting flavors and techniques into something that worked, and magically so. In July, Dallas' prodigal chef returned, opening Park on Henderson Avenue to almost instant success. The Dallas Morning News reported guests raising toasts to Cassel's chicken-fried steak. That's big news.