I got this recipe from Parents magazine. Supposedly, mushrooms have lots of vitamin D and potassium. I'm sure they are much healthier than pizza crust. I'm not going to say it tastes like pizza crust. It's definitely different but we all really liked it.
4 large portobello mushroom caps, stems removed
2 Tbs olive oil
1 8-oz can tomato sauce
1 clove garlic, minced
1/4 tsp dried Italian seasoning (or just sprinkle some stuff on them)
1/2 c shredded part-skim mozzarella cheese (I doubled the cheese)
1. Preheat over to 400. Line a 15x10x1 in baking pan with foil; brush lightly with olive oil. Place mushroom caps stem side down in prepared pan. Brush caps with remaining oil. Bake for about 10 min.
2. Meanwhile, in a small bowl stir together tomato sauce, garlic, and seasonings. Drain off liquid from mushrooms. Turn mushrooms stem side up. Spoon sauce into mushroom caps. Sprinkle with mozzarella cheese. Bake for 10 minutes.
My grandmother has made these with meat and spinach added too.