Stir together cocoa, hot water and oil.

In a separate bowl, mix next six ingredients to form dough. Add cocoa mixture to dough and mix five seconds, just long enough to marbleize.

Divide dough into four parts. Place on waxed paper and roll into logs about 20 inches long. Freeze two to three hours.

Preheat oven to 350 degrees Fahrenheit.

Slice each log into one- inch-wide slices. Place cookies on cookie sheet, leaving space between them, as they will expand.

Break each square of bittersweet chocolate into four or six little chunks. (You can use a knife to cut them up.) Place a chocolate square in center of each cookie.

Bake 12 minutes.