My meringue cookies look perfect–until I bake them and they flatten. What am I doing wrong?

The key to making meringue cookies is beating the egg whites. Here are some tips on the best way to beat egg whites:

1. Start with egg whites at room temperature.

2. Be sure the bowl and beaters are spotlessly clean. The James Beard award-winning baker and author Carole Walter recommends cleaning the bowl occasionally with lemon juice or white vinegar to prevent any film of oil from developing on the surface.)

3. Do not use aluminum or plastic bowls.

4. Be sure the eggs are at the soft peak stage before adding sugar."And be sure the egg whites look white, not yellow," says Michelle Tampakis, Senior Pastry Instructor at the Institute of Culinary Education.

5. Do not beat the eggs too quickly. This may be the most common mistake, and the one that causes meringues to deflate. When you whip whites at a high speed, says Chef Michelle, "both large and small air bubbles form and the large ones burst‚ which causes flattening." For more tips, watch our how-to video on making meringue cookies.

Recipe: Chocolate-Chip Meringue Cookies