Cut the stale bread into small cubes.
In a small bowl, combine about ½ cup of milk with the bread cubes to soak. Set aside.
Finely chop the onions and add them to a medium sized bowl.
Finely chop the parsley and add it to the same bowl.
Crack the egg right into the bowl.
When softened, take your hands to squeeze excess milk from the bread cubes and add them to the bowl.
Add the ground meat to the bowl. With your hands, mix all the ingredients until well combined.
Depending on your preference, with your hands form 8-16 meatballs.
Place them on a plate and set aside.
In a medium sized pot, heat up about 1 quart of bouillon or stock. When the bouillon is boiling, carefully add the meat balls, cover, and turn to a low simmer.
Simmer the meatballs for about 10 minutes or until done, turning them half way through.
With a slotted spoon, remove the meatballs from the pot, place on a plate and set aside.
Strain the cooking liquid through a strainer and reserve for the sauce.
Over medium-low heat, in the same or another medium sized pot, melt 2-3 tablespoons of butter. Add about 2-3 tablespoons of flour. With a wire whisk, combine the butter and flour well.
While stirring constantly, gradually add the reserved broth. Gently simmer to thicken the sauce.
Turn off the heat. Add 1 tablespoon of lemon juice, ½ cup of sour cream, 1 teaspoon of sugar, capers, and season with salt and pepper.
Taste the sauce and adjust seasonings to your liking.
Transfer the meatballs to the pot with the sauce and heat gently over low heat.
For the classic pairing serve with boiled potatoes. You can also serve the meatballs over rice, pasta, dumplings, or your favorite side.