There's butternut squash, leeks, and spinach as well as white beans in this hearty, rich, and flavorful vegetarian soup. It's a recipe that proves the slow cooker is as well suited to vegetable recipes as to big pieces of meat.
Place beans in a bowl; cover with 2 inches of water. Refrigerate, covered, overnight; drain and rinse. Cover with water in a saucepan. Bring to a boil; cook 10 minutes. Remove from heat; drain and rinse.
Place beans, oil, leeks, garlic, pepper flakes, squash, sage, and rind in a 5-to-6-quart slow cooker. Add 8 cups water. Cover and cook on low 6 hours. Remove and discard sage and rind; stir in lemon juice and spinach. Season with salt and pepper. Serve, drizzled with oil and topped with shredded cheese and pepper flakes.
Since raw beans can contain toxins, the FDA suggests soaking them overnight and boiling them before slow-cooking.