Portobello Mushroom Burgers

In the cookbook where I found this recipe for Portobello Mushroom Burgers, the author suggests that "portobello mushrooms are so meaty that many people mistake them for beef." Hmmm. Wonder if that would work on the kiddo?A conversation ensued:Kiddo: Mom, what's for dinner tonight?RG: Burgers.Kiddo: Yay!!They looked like beef burgers. The mushrooms are chopped up finely and blended with onion,