1. Wash rice thoroughly, rinse and bring to boil in 450 ml water. Reduce to simmer and cook covered for 10 minutes. Remove from heat and let soak for 10 more minutes. Pour rice into a clean bowl. Mix together sugar, salt and rice vinegar until dissolved. Pour the vinegar sauce over the rice, while constantly mixing up the rice to cool it.
2. Remove seeds from cucumber with spoon and cut cucumber into thin sticks. Cut prawns in half and 5 prunes into 20 quarters. Slice salmon to small strips and roll strips around 10 prune quarters.
3. Place seaweed sheet on a bamboo mat. Cover the nori sheets with ¼ of prepared rice, pressing rice together with hands. Leave an inch of the seaweed bare at the top. Dab a pinch wasabi paste 5 cm apart on the rice. Place ¼ of sushi ginger, 2 cucumber sticks, 4 prawn halves and 5 prune quarters on top. With the help of the bamboo mat, roll the seaweed sheet into a log. Slice log into 8-10 pieces with sharp knife. Prepare another nori sheet in the same way.
4. Arrange the remaining two seaweed sheets with rice and wasabi. Instead of prawns, place the salmon wrapped prune quarters on top. Roll into log and slice into sushi pieces. Put the remaining three prunes in a mixing bowl and puree bit by bit with soy sauce.

Serve sushi with prune soy sauce.