I got this baked mushroom recipe from Natalie Mikles, the Tulsa World food writer. You can check out her blog here. It's a great and inexpensive substitute for chicken parm!
2 large Portabella mushrooms (you may wish to gently remove gills with a spoon)
1 cup tomato pasta sauce, divided (I make this sugar-free sauce.)
4 fresh basil leaves, thinly sliced
1/4 teaspoon crushed red peppers flakes
1 cup (4 ounces) shredded part skim mozzarella cheese
1/4 cup (1 ounce) grated Parmesan cheese
Heat oven to broil, with top rack about 4 inches from broiler. Brush both sides of mushrooms with oil. Place mushrooms, gill side down, in a 9-inch baking dish. Broil for 4 minutes, remove and turn gill side up, broil 4 minutes.
Remove mushrooms from baking dish, drain excess liquid. Reduce oven to 400 degrees.
Spread 1/2 cup pasta sauce on bottom of baking dish, then place mushrooms, gill side up. Sprinkle with basil, red pepper flakes and the remainder of the pasta sauce. Top with mozzarella cheese and Parmesan; bake 5 to 10 minutes, until the cheese begins to brown. Remove and serve. Note: use at least part-skim mozzarella. Fat-free mozzarella is very rubbery when baked!