On those occasions when you find yourself with extra egg whites left over from a recipe calling for yolks, don't throw them away or give them to the dog: make meringues, those light-as-air, nonfat cookies that go together in a flash, then crisp up ever so gradually in a slow oven.

4 large egg whites
1/8 teaspoon salt
1/8 teaspoon cream of tartar
1/2 cup (3 1/2 ounces) Baker's Special, extra-fine, castor, or granulated sugar
1 teaspoon vanilla extract (or the extract of your choice)
sparkling sugar crystals

Preheat the oven to 250°F. Lightly grease (or line with parchment) two large baking sheets.

In a large bowl, beat the egg whites till foamy, then add the salt and cream of tartar. Add the sugar gradually, continuing to beat, until the meringue is thick and glossy, and forms stiff peaks. Stir in the vanilla or other flavoring at the end.

Drop meringue by tablespoonfuls (a tablespoon cookie scoop works well here) onto the prepared baking sheets. Sprinkle each with sparkling sugar crystals. Bake for 1 hour, then turn off the oven and let the kisses cool in the unopened oven (don't peek!) for 2 1/2 to 3 hours (1 1/2 to 2 hours for meringues that are chewy in the center, rather than crisp all the way through). Yield: about 30 meringues.