Place your ground beef in a bowl.

In a food processor, combine onions, garlic cloves, and spinach leaves.

Combine mixture into meat. Add your egg, salt, pepper, and parsley. Mix well.

In a separate pan, pour in olive oil and marinara sauce.

Shape the meat mixture into balls and place in pan with sauce. Fill empty marinara sauce bottle with cold water and pour over meatballs.

Cook for an hour and a half: first over a medium flame for 30 minutes, and then for one hour on low.