How to make
Soak the rice for 4 hours. Drain, and boil it. Once you've boiled it, drain it again, it is important for the rice to be dry because of the following treatment with the vinegar. Heat the vinegar with two tablespoons of brown sugar until the sugar is completely dissolved (about 2-3 minutes), then allow to cool for about 3 minutes and add it to the rice.
Allow the rice to cool down well. Peel the cucumber and avocado and cut them into thin strips. Carefully unfold a leaf of nori (seaweed) on a wooden lattice or a wet cloth. Spread a thin layer of rice on the entire leaf, leaving a distance of 0.5″ (1 centimeter) around the edges.
Arrange a row of cucumber, avocado and salmon on the rice. Carefully wrap the leaf into a roll. Roll up the rest of the leaves in the same way. Then place the rolls to harden in the refrigerator for about an hour.
Cut each roll with a sharp knife into 8 equal pieces. Serve with soya sauce and wasabi.