1. Heat oil in a large pot over medium heat. Add onions and garlic and cook until translucent, about 10 minutes.
2. Increase heat to medium-high, add sausage, salt, and pepper. Cook, breaking up sausage with a spoon, until golden brown, about 5-8 minutes.
3. Add sweet potatoes, broth, and water. Bring to a boil.
4. Add pasta and cook for 4 minutes. Reduce heat to low and add greens.
5. Cook until pasta is tender and greens are slightly wilted, about 4 minutes.
6. Serve with grated Parmesan cheese if desired.