1. Place squash cubes and garlic in slow cooker with 1/4 cup water. Cover and cook on HIGH for 3 hours or on LOW for 5 hours or until squash is tender.
2. Meanwhile, heat oil in a medium-size nonstick skillet over medium-high heat. Cook onion in skillet for 5 minutes or until softened. Stir ginger into skillet and cook 1 minute.
3. Heat oven to 350 degrees. Remove squash from slow cooker using a slotted spoon and discard garlic and remaining liquid in slow cooker. Puree half of squash in blender or food processor with half of onion mixture and 2 cups of the broth until completely smooth; pour into slow cooker and repeat with remaining squash, onion mixture, 1 cup broth and 3/4 cup water. Stir in salt and pepper, then cover soup and cook an additional 30 minutes or until hot.
4. While soup is heating up, if desired, place bread slices on a baking sheet and top each with 1 teaspoon cheese. Bake at 350 degrees for 15 minutes or until lightly browned. Place 1 bread slice on top of soup in each serving bowl.