Heat oil in a large saucepan over medium heat. Add chopped onion, cumin, and garlic; sauté 6 minutes or until tender. Add squash cubes, and cook 2 minutes, stirring frequently. Add broth, beer, and salt; bring to a boil. Cover squash mixture, reduce heat, and simmer 30 minutes or until squash is tender.
Place squash mixture in a blender, and process until smooth. Return squash mixture to pan, and cook until thoroughly heated. Ladle soup into individual bowls, and top with yogurt.