Heat oven to 275°F. Line cookie sheets with parchment paper or grease and flour cookie sheets. In small bowl, beat egg whites and cream of tartar at medium speed until soft peaks form. Gradually add 1/2 cup sugar, beating at high speed until stiff peaks form. Drop mixture by scant teaspoonfuls onto paper-lined cookie sheets.
In medium bowl, combine all filling ingredients except walnuts; mix well. Stir in walnuts. Drop 1/2 teaspoon filling onto each cookie.
Bake at 275°F. for 30 minutes. DO NOT OPEN OVEN. Turn oven off; leave cookies in oven with door closed for 10 minutes. Remove from oven; cool completely. Remove cookies from paper.