Here's Chris Nuttall-Smith's review of the place:
I've been to the Vancouver location of Hapa many times, and visited the Toronto location for the first time about a week ago. I have to say I agree with Nuttall-Smith. Whereas I've always enjoyed the Vancouver Hapa, the Toronto restaurant left me wanting.
The menu is filled with items like the tuna avocado "salsa with plantain chips, or the halibut "taco" (served with a disappointing store-bought type tortilla) that make it feel like the Toronto location is trying a little too hard to play to a "western" crowd.
And the ambience - the Vancouver restaurant on Robson, for example, is a warm, beautiful space - is lacking in TO too. The front area is filled with televisions playing sports games, which really takes away from the overall atmosphere.
For my money, I'd take either of the Guu locations over Hapa any day.
You can find freeze-dried corn at Whole Foods (I think it says that in the book too, which is how I knew to go there).
I've also seen it for sale at the Fresh & Wild at King and Spadina.