Mushrooms are the craziest little things. In a package or loose, they seem so dry, but stick them in a saute pan for a few minutes and suddenly they're moist and delicious! The same thing happens when you chop them up in a food processor. I thought I would need to add more sour cream to bind the mushrooms together, but those crazy little mushrooms handled it on their own.
I could happily eat this on toasted french bread every single night. It would be delicious warm, too -- just assemble the canapés and toast them on a low setting for 5 minutes. YUM!