Place the beef and pork mince in a large bowl and add the onion, garlic, breadcrumbs and dried herbs. Season with salt and freshly ground black pepper and mix well with clean hands. Divide the mixture into 20 portions and roll into small, neat balls.
Heat the sunflower oil in a large non-stick frying pan and fry the meatballs for 6–8 minutes, or until nicely browned on all sides. Roll the meatballs around in the pan as they brown to prevent them from becoming flattened on one side. (You may need to do this in batches.) Transfer the meatballs to a large lidded saucepan.
To make the gravy, heat the sunflower oil in the frying pan and gently fry the onion over a low heat for five minutes, or until softened, stirring regularly.
Sprinkle the flour into the pan and stir well. Slowly add the red wine, stock and tomato purée, stirring constantly.
Pour the gravy over the meatballs and bring to the boil. Reduce the heat, cover the pan with a lid and leave to simmer gently over a low heat for 30 minutes, stirring occasionally.
Remove the lid and increase the heat. Boil the gravy for another 3–5 minutes or until thickened. Season, to taste, with salt and freshly ground black pepper and serve.