1. Prepare the kuzu-water (starch-water). Put the kuzu-ko into a small bowl, add water and stir.

2. Put the sesame paste into a small ovenproof bowl (15cm across). Add 1Tbsp kuzu-water, stir with a whisk until creamy. Add another Tbsp kuzu-water, stir well until smooth. Make sure the sesame paste and kuzu-water are completely mixed without separating. Add the rest of the kuzu-water and mix.

3. Cover with the edge-open wrap and microwave on 600W for 1minute. (30seconds on 1200W) Remove the wrap and stir with a whisk.

4. Microwave on 600W for another 1 minute (30seconds on 1200W) without covering. Stir again until smooth.

5. Prepare 2 sheets of 25cm square cut plastic wrap. Put 4) evenly on each sheet. Close the wrap and tie with rubber band. Put them into cold water (with ice cubes), chill for 20minutes.Remove the wrap, and arrange them on dish.

6. Garnish with grated wasabi, pour on some kombu-soy sauce and serve.

For how long you should cook with your microwave oven, see Cooking Time vs Wattage Conversion.
For more tips of using Microwave Oven, see Sachiko's Guideline to Microwave Cooking.