On cookie sheet, unroll both dough sheets, overlapping long sides to make 15x13-inch rectangle; press seam to seal. Spoon chicken mixture down center of rectangle in 6-inch-wide strip. Using kitchen scissors or sharp knife, make cuts 1 inch apart on each long side of rectangle to within 1/2 inch of filling. Fold strips of dough diagonally over filling, alternating from side to side and pressing to seal. Brush with beaten egg white.