I just made portobello mushroom burgers as per this recipe and they were in-cred-ible. Now, this statement is coming from someone who has never eaten a portobello mushroom burger she liked. I also made the buns (equally as delicious) earlier today using this recipe.
We added about 0.5 teaspoons of cumin seeds to the marinating mixture and used spinach leaves and mozzarella cheese as toppings.
Feast your eyes upon its deliciousness.