1. Add the water, carrots and potatoes to a large saucepan and bring to a boil.
2. In the meantime, heat the olive oil in a large frying pan and saute the onion and garlic for 3-4 minutes.
3. Add the 3 tablespoons of flour and paprika and cook for 3 minutes more, while stirring with a wooden spoon.
4. Ladle some liquid from the saucepan and pour it slowly in the frying pan, while using a whisk to break all the lumps from the flour.
5. When the thickening mixture is smooth, add it to the saucepan.
6. Let the soup simmer until you are ready to add the meatballs.
How to make the meatballs:
7. Add the ground beef, egg, dried basil, and ground flax seed to a large mixing bowl and mix them until smooth.
8. Form small meatballs and roll them in the remaining flour before adding them to the soup.
9. Add the meatballs one by one, so as not to stop the cooking of the soup by dropping its temperature too fast.
10. Simmer the meatball soup for 10-15 minutes more.
11. Add the washed spinach 5 minutes before the soup is ready.
12. Season the meatball soup with salt and pepper to taste and let it stand for 10 minutes before serving.
13. Top the soup with shredded cheddar cheese, if desired.