Cookie

The cookie is an edible item introduced in the Beta 1.4 update. Notch had previously mentioned it in a tweet. It requires Cocoa Beans to craft. It was later confirmed that cocoa beans would appear in dungeon chests. A full stack of eight cookies restores a total of four Hunger points (the same amount of hunger points as one Cooked Porkchop).

Advantages

 * Eating a cookie will restore half a hunger point. This is useful if you want to completely fill your hunger bar without wasting the healing potential of a more potent food.

Disadvantages

 * A single cocoa produces enough cookies to restore the hunger meter as much as one cooked porkchop. However, porkchops are much easier to acquire, and a single porkchop is easier to eat than eight cookies.
 * A full stack of cookies heals a total of 32 hunger points, whereas a full stack of cooked porkchops heals 256 hunger points. For comparison, you'd need 512 cookies (64 full stacks of 8) to heal 256 hunger points, which would only be portable if you carried a workbench, one stack of cocoa beans, and two stacks of wheat.
 * Cocoa Beans can only be found in dungeons at the current time, making cookies highly inefficient, on par with apples.
 * Although the ingredients for cookies are a better use of stackable inventory space than the ingredients for bread, they're still not the best. 64 bowls of Mushroom Stew yield 320 hunger points. However, Mushroom Stew doesn't stack, so the ingredients (red and brown mushrooms and at least one bowl) must be carried separately. Because Mushroom Stew can be crafted on the 2x2 inventory crafting grid, it is a much more efficient hunger point resource than cookies, and since the bowl is reusable, it scales up better if you want to devote more than four inventory spaces to your food supply. Also, unlike cocoa beans, mushrooms are a renewable resource.
 * When cookies were first introduced, they had the distinct advantage of being the only food that could be stacked in its ready-to-eat form. They were given a limit of eight per stack to keep them from becoming too overpowered, since at the time, food worked by healing damage instantly. When hunger was introduced, eating became more time-consuming, and food-related health regeneration was capped at a rate of half a heart every four seconds. Also, when most food became stackable up to 64, cookies kept their limit of 8, so their biggest advantage turned into a huge disadvantage.

Trivia

 * Before Beta 1.8, cookies were the only food that could be legitimately stacked (up to 8).

Bugs

 * If you click on the cookies (the crafting result in the crafting menu) while holding shift, it's possible to exceed the stacking limit of 8.