Stuffed Portabello

I bought 2 large portabello mushrooms the other day and decided to stuff them as a side for dinner.  They were so filling they could have been dinner itself.  The filling can be used to stuff smaller mushrooms for an appetizer...just reduce the cooking time a bit.

2 large portabella mushrooms
5 - 6 oz. frozen chopped spinach, thawed and squeezed dry
1 egg, slightly beaten
1/4 cup sour cream
1 green onion, finely sliced
1/2 cup crushed croutons
1/4 cup feta cheese, crumbled
1/4 tsp. granulated garlic or garlic powder
1/4 tsp. each salt and pepper
1 cup shredded mozzarella, divided

Clean the mushrooms by removing the stems and scraping out the gills.  Brush the caps with a little olive oil and set them cap side down in a baking dish.

For the filling:
Combine all other ingredients, reserving 1/2 cup of the mozzarella. Divide the mixture evenly in the mushroom caps.
Bake, uncovered at 350F for about 30 minutes. Sprinkle the reserved 1/2 cup cup cheese over the tops and bake about 10 minutes more.