I've never found a wasabi powder that is strong enough. It kind of just limps along.
Most wasabit powder or paste that I find doesn't really have wasabi in it - it is horseradish tinted green. Currently I am on a quest for the real deal. If it is real, either one would be great.
Here is an interesting link with Japan Times which shows wasabi root - and other interesting spring vegetables of Japan. http://search.japantimes.co.jp/cgi-bin/fg20110422f1.html
One more thing (can you tell I am into this?) here is a link that comments on real wasabi and where to get it in our area. http://www.chefseattle.com/blog/food/real-wasabi/
Thespicehouse.com carries real wasabi (known as namida)...$8.49 for 1/2 an ounce.
I have found that the powder can get very bitter if not mixed in the exact proportion so I use it with other ingredients as a last measure. I think the wasabi paste is the safer option.
One thing about the powder is that really needs to be fresh and stored well.
One another trick is that the more you stir it...the hotter it gets.
I make mine kinda soupy at first..stir, stir, stir, let it rest and add more powder to consistency and let it rest a bit more.
Same goes for Coalman's dry mustard when making hot mustard sauce for egg rolls.
Try it; just mix some up just to incorporate and taste.
Then stir the heck out of it and let it rest 15 mins in the fridge and taste again. Whooo! Tears.
@SKK Whole foods (at least mine) serves real wassabi in house at their sushi bar.
There's a suppler in NC that grows the roots. And ships online. (tho you might some need some friends to share that pricey item)..they also sell dried 'real wasabi'.
I love my jar of wasabi powder from penzey's spices. I agree with sam1148...the more you stir it, the better it gets! When I first started using it to make wasabi mayo for my WOMBAT (Wasabi Olive oil Mayo, Bacon, Avocado, and Tomato) sandwich, I was just adding the powder to the mayo and it took far too much to get any heat...then I read the directions on the side of the jar...well....
But i found a funny little item when I went to the penzy's site to see what their wasabi powder was made of (ashamed to say, I thought it was wasabi!)
Here is what they say: (www.penzysspices.com)
Funnily enough, the wasabi we've all been eating in Japanese restaurants for many years isn't actually made of only ground up wasabi root. It is a combination of ingredients which combine to give the bright heat and zesty flavor we all know and love mixed with soy sauce and served with sushi. Pure Wasabi root is extremely expensive and a small jar doesn't really make very much. As far as the flavor difference, it is kind of like turtles. When you've been going to the candy store all your life eating turtles, luscious chocolate covered caramel and pecan creations, and then you get told no, real turtles are at the pet store - so you go there and find out they are crunchy reptiles, even though they truly are the "real" turtle, you'll probably, in the long run, end up back at the candy store.
Natural Wasabi - Blend of horseradish, mustard, tapioca starch and wasabi.
oops...forgot to say you need to reconstitute it with water, then add it to the other ingredients...again with the reading!