Ingredients

　　4 large egg whites

　　1 cup sugar

　　Pinch of cream of tartar

　　1/2 teaspoon pure vanilla extract

　　Put egg whites, sugar, and cream of tartar in the heatproof bowl of an electric mixer set over a pan of simmering water. Cook, whisking constantly, until sugar has dissolved and mixture is warm to the touch, 3 to 3 1/2 minutes. Transfer bowl to electric mixer fitted with the whisk attachment; beat, starting on low speed and gradually increasing to high, until stiff, glossy peaks form, about 10 minutes. Add vanilla; mix until combined. Use immediately.

　　Martha Stewart's Cookies