In the 2-cup/500 mL Micro Pitcher Set, stir together sugar and water. Microwave on high power 45 seconds, or until sugar has dissolved. Remove from microwave, set aside.
In the base of the Power Chef® System fitted with blade attachment, add potatoes, cocoa powder and simple syrup. Cover and pull cord until well blended and almost smooth. Transfer mixture to a Freeze-It® Medium Shallow Rectangular Container. Seal and freeze at least 6 hours or overnight.
Remove Freeze-It® container from freezer; let stand at room temperature 5 minutes. Using a butter knife, gently break mixture into 2–3″/5–7 cm pieces. Place medium bowl or Freeze-It® container below Sorbet Maker spout. Fill sorbet hopper with frozen chocolate base pieces. Place plunger on top of frozen chocolate. Place plunger on top of frozen chocolate. Gently push down on the plunger while turning handle to process. Repeat with remaining fruit.