Sea salt and freshly ground black pepper, to taste
Method
Preheat the oven to 225°C.
Place the beef bones, carrots, onions, bay leaves and celery in a roasting tray. Coat the ingredients with the tomato paste, then roast for 40 minutes, or until golden brown.
Place the bones and vegetables in a large saucepan, then heat the roasting tray on the stove top. Once the tray is hot, pour in 1 cup water and scrape the tray using a wooden spoon. Pour the water into the pot, cover with the remaining water and add the Parmesan rinds. Bring to the boil and simmer for 5 hours. Strain the broth in a large bowl.
To make the barley risotto, heat the olive oil in a large saucepan, then add the onion and garlic and sauté until golden.
Add the barley, then add 1 cup broth and cook until absorbed. Repeat with the remaining broth and cook until the barley is al dente.
Stir in the butter and Parmesan and season to taste. Ladle over more stock and serve with the kale.
Cook's note: Keep the rinds of wedges of Parmesan to add nutty flavour to soups and broths.