In saucepan, combine rice and 1 1/4 cups (300 mL) water; bring to boil. Cover and reduce heat to low; cook for 25 minutes or until rice is tender.
With fork, stir in rice vinegar and sesame seeds.
Meanwhile, line an 8-inch (1. 2L) round or an 8-inch square cake pan with plastic wrap. With spatula, press rice firmly and evenly into pan. Let cool completely. Turn out onto flat serving plate.
Top the rice with a layer of avocado slices.
Using scissors cut nori into thin strips; sprinkle over avocado.
Arrange crabmeat, cucumber and ginger over top.
Stir together mayonnaise, milk and wasabi powder; drizzle over top.