For the ragu, heat the oil in a frying pan and fry the onion and garlic for 2-3 minutes, or until the onion is soft. Add the beef and fry for 5 minutes, or until browned. Add the chopped tomatoes, tomato puree, mixed herbs and stock. Simmer for 15 minutes, or until the sauce develops a thicker consistency. Season to taste with salt and pepper.