Heat a large non-stick frying pan over medium heat. Add the butter, oil, garlic and mushrooms and cook for 5 minutes or until the mushrooms are golden. Preheat the oven to 180°C (355°F). Place the rice, stock and mushroom mixture in a 22 x 30cm (8½ x 12 in) 10-cup (80 fl oz) capacity baking dish and stir to combine. Cover tightly with foil and bake for 40 minutes or until most of the stock is absorbed and the rice is al dente. Add the parmesan, butter, salt and pepper and stir until the butter is melted. Serve immediately. Serves 4.