I'll second the Soma vote. Their chocolates are fantastic. They roast and mill their own cocoa beans.Check out Soma in the Distillery District - it's the chocolate equivalent of single malt scotch. Pricy but amazing. I found their hot chocolate to be way too sweet for my palette, but everything else I've tried is exquisite.
They also have a store on King St. W at Brant (1 block west of Spadina).