You can be sitting in a high chair or in a high-style Italian chair, and if someone sets a bowl of mac and cheese in front of you, you're bound to be delighted. This humble bowl of mostly white ingredients is currently the most sought-after comfort food on American tables. It suits everyone: teens, vegetarians, lumberjacks, sophisticates.Mac and cheese is on many restaurant menus, partly because of the economy, mostly because customers love it and want it. The dish went from the home to the professional kitchen (dishes usually travel the opposite way: from chefs to home cooks). And because...