Heat oven to 300°F. Cover cookie sheet with nonstick silicone pad or parchment paper.

Using a mixer, beat the egg whites and cream of tartar together in large bowl at high speed until soft peaks form. Gradually add sugar a little at a time, then vanilla, beating well after each addition until you get stiff peaks, the sugar is dissolved and the mixture is glossy.

Fold in mint chocolate chips. Drop mixture by tablespoons onto cookie sheet.

Bake 35 to 45 minutes or just until dry. Cool slightly; remove from cookie sheet.

Cool completely on wire rack. Store covered, at room temperature. Makes about 30 cookies.