Confectioners' sugar is used in cookies where tenderness and a fine crumb are important. Confectioners' sugar is made by pulverizing granulated sugar and combining it with a little cornstarch (about 3 percent of the total weight) to prevent it from clumping together. Because of its fine, powdery consistency, this sugar gives cookies a melt-in-your-mouth texture. Note that small lumps can still form in the box, so we recommend sifting confectioners' sugar before combining it with other ingredients.

VANILLA EXTRACT When we tested vanilla extracts several years ago, the results were so shocking we repeated the test again and again. It turns out that most people, including pastry chefs, can't tell the difference between a cookie made with vanilla extract and a cookie made with the imitation stuff, which is derived from wood pulp. The differences are apparent in a custard, but in a cookie the quantities are so small and the other ingredients are so flavorful that these differences are hard to detect. But since we are generally loath to recommend ersatz products and since the price differential between the real and the fake is fairly small, we opt for the real thing in this case, too, even if it's hard to taste the difference.

KEY EQUIPMENT

Cookie-making requires very few pieces of equipment. You can even get away with using a wooden spoon instead of an electric mixer, although we do prefer a mixer. The rest of the equipment can be purchased for less than $15, total.

COOKIE SHEETS We tested eleven sheets in a variety of materials and came to some surprising conclusions. First of all, shiny, light-colored sheets do a better job of evenly browning the bottoms of cookies than dark sheets. Most of the dark sheets are nonstick and we found that these pans tend to overbrown cookies. Shiny, silver sheets heat much more evenly, and if sticking is a concern we simply use parchment paper.

In our testing, we also came to prefer sheets with at least one rimless edge. This way we could slide a whole sheet of parchment paper onto a cooling rack without actually touching the hot paper. The open edge also makes it possible to slide cookies on a rack, rather than lifting them onto the rack and possibly dropping them. Our favorite cookie sheet is made by Kaiser out of tinned steel. At just $7, it was also the cheapest sheet we tested.

COOLING RACKS These often-neglected items are essential because they allow air to circulate under and around the cookies as they cool. Cookies cooled on a closed sheet might stick or become soggy. Choose a cooling rack that is large and sturdy. Some models have thin wires running in a single direction, but we prefer racks with crosswoven pieces of metal that form a fairly tight grid. These racks, sometimes called icing racks, are usually fairly sturdy. Also, the holes in the grid are very small, making it impossible for cookies to slide through onto the counter, something that often occurs on racks with wires that run in just one direction.

MIXER There are two basic types of mixers. Handheld mixers lack the power to knead bread (you need a standing mixer for that) but are fine for cookie doughs.

When shopping for a handheld mixer, look for models that have thin, curved wire beaters rather than the old-fashioned kind with thick posts down the center. This new design does a better job of driving food down into the bowl, improving the efficiency of the mixer while reducing splattering. Wire beaters are also much less likely to become clogged when mixing stiff cookie doughs.

In our testing, we also found that handles that slant up to the front fit the hand better and reduce arm stress more than handles that are parallel to the mixer. We tested nine mixers and found the KitchenAid to be the best choice.

Although standing mixers are not essential for making cookie doughs, they work well and free the cook to gather ingredients or grease a cookie sheet. When selecting a standing mixer, choose one with a single wide, flat beater rather than the two metal beaters commonly found on handheld mixers. The Rival Select and KitchenAid standing mixers have these flat beaters, which operate by planetary action. These beaters are designed to reach the sides and bottom of the bowl to gather up and combine ingredients.

PARCHMENT PAPER When sticking is a potential problem, we recommend lining cookie sheets with parchment paper. The paper also keeps the bottom of the cookies from overbrowning. When the cookies are baked, we usually slide the whole sheet of parchment, with the cookies still attached, right onto the cooling rack. When cooled, the cookies can be peeled away from the paper.

Even when sticking is not an issue, we still use parchment paper. It makes cleanup a snap, and we can reuse cookie sheets for subsequent batches without having to wash them first. When parchment is essential, the recipe directions call for it. Otherwise, use parchment at your discretion.

MIXING COOKIE DOUGH

Most cookie doughs are prepared in the same fashion. The butter is creamed with the sugar until light and creamy. The eggs and other liquids (vanilla or other extracts) are added. Finally, the flour and other dry ingredients, which have been sifted or stirred together, are added.

This process sounds easy (and it is), but there is some important science here. The butter must be properly creamed in order to incorporate the right amount of air into the fat. In our tests, we've consistently found that cookies made with creamed butter are higher and have a lighter texture than those made with butter that is not creamed. We also found that creaming the butter with sugar adds more air than beating the butter alone. That's because the sharp edges of the sugar crystals physically aerate the butter by cutting small air pockets in the fat.

Cookies made with cold butter are often flat because the creaming process was not able to whip enough air into the butter. Ideally, an hour or two before you want to make cookies, remove the butter from the refrigerator and let it warm to about 65 degrees. Butter starts to melt at 68 degrees, so the stick should still be a bit firm when pressed.

If you have forgotten to soften the butter, don't use the microwave to bring it up to room temperature. The microwave will melt the butter in places. Instead, cut the butter into very small bits so they will warm up quickly (see figure 3). By the time you have preheated the oven and assembled and measured the remaining ingredients, the butter should be close to 65 degrees.