Preheat oven. In double boiler, over hot, not boiling, water, melt 1 (6 ounce) package semi-sweet chocolate pieces. Remove from water and COOL, about 5 minutes. Meanwhile, in medium bowl, with electric mixer at high speed, beat 3 egg whites and 1/2 teaspoon vanilla extract until soft peaks form; gradually beat in 1 cup granulated sugar, until mixture is very stiff. Fold in 1 cup finely crushed Saltine crackers and chocolate. Drop by level teaspoonfuls onto greased cookie sheets. Bake 10 minutes or until tops are crisp when touched with finger. Remove from sheets at once; cool. Makes about 4 1/2 dozen.