3 cups shredded part-skim mozzarella, divided
15 whole-wheat lasagna noodles (about 12 ounces), uncooked
Pinch of crushed red pepper (optional)
3 cloves garlic, minced
1 28-ounce can diced tomatoes
1 28-ounce can crushed tomatoes
1 small zucchini, quartered lengthwise and thinly sliced
3 large or 4 small portobello mushroom caps, gills removed (see Tip), halved and thinly sliced
1 5-ounce package baby spinach, coarsely chopped
1 15- to 16-ounce container part-skim ricotta
1 large egg