Risotto al Salto from The River Café Cookbook by Rose Gray and Ruth Rogers

Ingredients

• sea salt and freshly ground black pepper
• 2 tablespoons olive oil
• 300 g (10 oz) risotto rice
• 1 beef or veal shin bone, cut open at both ends to reveal the marrow
• 120 g (4.½ oz) butter, at room temperature
• 1 litre (1.¾ pints) Chicken Stock
• Parmesan, freshly grated
• 1 medium red onion, peeled and very finely chopped