Meatball soup with egg-lemon sauce (Youvarlakia soupa avgolemono)

This is a delicious main dish soup, served with bread, a piece of feta cheese and a nice salad.

500 g ground beef
1 small onion, grated
salt & pepper to taste
2 Tablespoons olive oil
3 Tablespoons chopped parsley and/or mint leaves
6 Tablespoons uncooked rice
1 egg, lightly beaten
4 Tablespoons flour
2 l water (more if needed)

For the egg-lemon sauce:
2 large eggs
juice of 1 lemon

Mix together the ground beef, onion, oil, salt, pepper, herbs, 3 tablespoons of the rice, and the egg. Roll the mixture into about 15-20 meatballs. Sprinkle the flour onto a flat plate and roll the meatballs in the flour until lightly covered.
Bring the water to a boil and drop the meatballs in. Cook about 15 min., covered. Add the rest of the rice and continue cooking 15-20 min. longer, adding water if necessary. Season with salt and pepper if needed.
Remove the pan from the heat. Remove 4 ladlefulls bouillon from the pot and place in a bowl. Separate the eggs and beat the egg whites + 2 tablespoons water in a separate bowl until stiff. Fold in the egg yolks and lemon juice, and add the 4 ladles of bouillon. Do this carefully to avoid curdling the eggs. Pour the egg mixture back into the soup pot, stirring thoroughly but gently, and serve immediately.