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["Sift together flour and cornstarch onto a sheet of waxed paper.", "Set aside.", "Beat butter and confectioners' sugar in a medium bowl until blended.", "Stir in vanilla.", "Gradually beat in flour mixture to make soft dough.", "Divide dough in half.", "Knead cocoa powder into 1/2 of dough in bowl.", "Flatten both doughs; wrap separately in plastic wrap or waxed paper.", "Chill 1 hour or until easy to handle.", "Roll each batch of dough between 2 sheets of wax paper into 10"" square.", "Push sides in to make absolutely even, using ruler or long-bladed knife.", "If dough becomes too soft or sticky, refrigerate on cookie sheet.", "Remove top sheet of wax paper from nonchocolate dough; brush top with egg white.", "Remove paper from top of chocolate dough; invert onto nonchocolate dough, matching sides up exactly.", "Peel off remaining sheet of wax paper.", "Cut into 4 equal strips, each 10 x 2 1/3"".", "Brush lightly with egg white.", "Stack dough strips neatly to make 8 alternating layers.", "Wrap stack in plastic wrap.", "Chill several hours or overnight.", "Dough can be refrigerated for up to 1 week.", "Preheat oven to 375 degrees Fahrenheit.", "Cut dough crosswise into slices slightly less than 1/4"" thick.", "Place slices on cookie sheets 1"" apart.", "Bake 10 minutes.", "Transfer cookies to wire rack to cool completely.", "Store cookies in tightly covered containers in cool, dry place."]
