Cooking Mama does what it sets out to do very well.
The game is nothing more than a set of casually laid-out challenges where each "level" is a certain meal. It can be as simple as making instant ramen to something more involved like pork curry and rice. Each step in the recipe has been paired down into a touch-screen mini-game. Most are simple: slicing an onion on the lines, or quickly chopping chives, or shredding some garlic. The complex tasks are the ones you have to watch out for: cutting tough meats, weighing specific ingredients, diced vegetables, or performing specific tasks in "rhythm." Even though most of the game is a simple matter of paying attention and following the instructions, the tougher techniques can turn a gold metal meal into a bronze medal.
The big question: is any of this fun? Though the entirety of this game is simply doing what you're told as quickly as possible, it's actually an amusing game if you're not expecting much out of it. More importantly, though, it's been well-designed as a portable game, as the developers have given it a good "pick up and play" presentation: turn on the system, make a dish, get your rank, turn it off. All progress is saved, and the more dishes you complete the more that become available. So there's a discovery element to Cooking Mama: what sorts of dishes are hidden to unlock? It also has a bit of challenge due to a "margin of error" element -- as good as you are at following directions, there's that one portion that can screw up that important gold medal.
And as you add more recipes to the queue, you're also building up the skill set of mini-challenges that can be practiced and played outside of the cooking "game." Here, you can try and top the high score or go for the maximum, and if you pull off the top score possible it'll be noted with a nice, satisfying chef hat. For a simple set of touch screen challenges, the designers give the production a good amount of legs. A nice bang for the twenty bucks.