Robert Irvine tests his mettle in Downey, Calif., with a super spicy burrito stuffed with succulent marinated chuck roast and creamy nacho cheese. Then, in Denver, a decadent dark chocolate cake is pushed to new heights with whiskey, cherry pipe tobacco and hot chile peppers. Finally, in St. Louis, a noodle dish is smothered with Korean and Mexican sauces so seriously spicy, it's gone nuclear.