-chopped (2 oz ea; opt) Preheat oven to 200'F. Line baking sheets with parchment paper. In large mixer bowl, combine egg whites and cream of tartar. Beat at highest speed of electric mixer until mixture is just frothy. Add sugar, 1 tablespoon at a time, beating well after each addition. Beat until stiff peaks form. Add vanilla; beat 1 minute. Fold in chocolate chips. Drop mixture by teaspoonfuls, 3 cm apart, onto prepared baking sheets. Bake 2 hours or until meringues are thoroughly dry to touch but not browned, rotating baking sheets halfway through baking. Turn off heat. Leave in closed oven 3-4 hours or until completely dry. Remove from oven. Cool completely. Carefully remove from parchment. Melt white chocolate in top of double boiler over hot, not boiling, water. Stir constantly until chocolate melts. Dip top of each cookie into melted chocolate, if desired. Place on waxed paper to dry. Store at room temperature in tightly covered containers. Makes about 6 dozen cookies.