Barley Squash Gratin

Name: Barley-Squash Gratin
Ingredients: 2 pounds butternut squash, peeled, halved, seeded and cubed (about 5 cups); 1 (10 ounce) package frozen chopped spinach, thawed and well drained; 1 medium onion, cut into wedges; 1 cup regular barley (not quick-cooking); 1 (14 ounce) can vegetable broth; ½ cup water; 3 cloves garlic, minced; ¼ teaspoon ground black pepper; ½ cup shredded Parmesan cheese (2 ounces)