Slow-Cooker Vegetable and Pumpkin Lasagna

INGREDIENTS

• 2 jars (each 24 oz.) pumpkin Parmesan pasta sauce
• 2 cups water
• 4 Tbs. olive oil
• 1 lb. spinach
• 2 small yellow onions, thinly sliced
• 2 lb. cremini mushrooms, quartered
• Kosher salt and freshly ground pepper, to taste
• 15 ruffle-edged lasagna noodles (not no-boil noodles)
• 2 cups béchamel sauce (see related recipe at left)
• 1 1/4 lb. mozzarella cheese, grated
• 1 oz. Parmigiano-Reggiano cheese, finely grated