Bupo - you can find wasabi powder in most grocery stores in with the other Asian food. You just mix equal parts powder and water - let rest about 10 minutes, then use. I have used both the powder and the tube of wasabi - they are both good.
I just took some chicken thighs out of the freezer to cook tonight - I think they are going back in - I'm going to make these!!!!
Edited to say - I see I don't have enough time to make these - but one night next week!!!! Even if I just do the fried oysters and nothing else they would be good!!!
"Count yourself...you ain't so many" - quote from Buck's Daddy