Combine all ingredients except the egg and spaghetti in the slow cooker. Cook on low for 3+ hours.
2. Add the spaghetti and cook for another 30 minutes.
3. Beat the egg and slowly drizzle into the soup shortly before serving.
4. If preparing on stove top, saute onions and garlic first, then the rest of the vegetables. Add broth, then tofu. Use the same instructions for the spaghetti and egg.