1/2 cup sugar
1 teaspoon vanilla
1 1/2 cups all-purpose flour
1/2 teaspoon baking powder
1/4 teaspoon salt
1 (1-ounce) square unsweetened baking chocolate, melted, cooled
1 teaspoon instant espresso powder
1 tablespoon freshly grated orange zest
Combine sugar, butter, egg and vanilla in bowl. Beat at medium speed, scraping bowl often, until creamy. Add flour, baking powder and salt; beat at low speed, scraping bowl often, until well mixed.
Combine melted chocolate and espresso powder in another bowl. Add half of dough to chocolate mixture; beat until well mixed. Add orange zest to plain dough in bowl; beat until well mixed.
Shape each half into 4x5-inch rectangle; wrap in plastic food wrap. Refrigerate 2 hours.
Roll out chocolate dough between two sheets of lightly floured waxed paper to 12x7-inch rectangle. Repeat with orange-flavored dough. Place orange-flavored dough on top of chocolate dough; gently press doughs together. Roll up, jelly-roll fashion, starting with 12-inch side. Wrap in plastic food wrap. Refrigerate at least 2 hours until firm.
Heat oven to 375°F.
Cut rolls with sharp knife into 1/4-inch slices. Place 1 inch apart onto ungreased cookie sheets. Bake 7-9 minutes or until set. Remove from cookie sheets; cool completely.
To keep cookies round when slicing, turn roll 1/4 turn after each slice.