2) Using your hands, gently form the meat mixture loosely into meatballs approximately 2cm in diameter. (Packing the meat mixture too tightly together will result in tough meatballs). Put on a baking sheet, cover and refrigerate for at least one hour or up to 24.
3) For the Soup: Heat the three tablespoons of the olive oil in a large pan over medium heat. Add the meat balls and brown, turning occasionally. Transfer meatballs to a platter and set aside.
4) Heat the remaining two tablespoons of oil to the pan and add the onion, celery and carrot. Cook, stirring occasionally, until soft and golden, about ten mins. Add the garlic, thyme, and red pepper and cook for another three minutes.
5) Stir in the escarole and cook until just wilted, about two minutes. Add the chicken stock and tomatoes and bring to a gentle simmer. Return the meatballs to the pot, cover and cook for ten minutes, stirring once or twice. Season with salt and pepper, to taste.
6) Ladle the soup into warm bowls. Drizzle over some olive oil and sprinkle a little Pecorino over each serving.