1. On waxed paper, sift together flour, baking powder and salt; set aside.

2. In small bowl with electric mixer at medium speed, beat butter and sugar until light and fluffy. Beat in eggs, orange peel and vanilla. Blend in flour mixture on low speed.

3. Remove half the dough; set aside. Add melted chocolate to dough in bowl; beat until combined.

4. Roll each piece of cookie dough between sheets of waxed paper to a 12 x 9 inch rectangle. Slide a cookie sheet under each rectangle and freeze dough 15 to 20 minutes.

5. Remove chilled cookie doughs and peel off top pieces of waxed paper. Flip chocolate layer onto plain layer, making sure edges are even; trim, if necessary. Peel off remaining waxed paper. Starting at short end, tightly roll the two layers together jelly-roll fashion. Wrap in plastic wrap. Freeze several hours or overnight.

6. Preheat oven to 350 degrees.

7. Slice cookies to 1/4-inch thickness; place 1 inch apart on ungreased cookie sheets.

8. Bake 18 to 20 minutes or until edges are lightly browned. Cool on wire racks.