Step 1: Heat 50g butter in a large, shallow, wide-based saucepan. Add the onion and sauté over a low to medium heat until golden.
Step 2: When the onion is cooked, add the rice and stir to coat with the onion mixture. Cook for 1-2 minutes, then increase the temperature to high.
Step 3: Make a well in the centre of the rice and add 100mL of Verjuice, continuing to stir until the liquid is absorbed.
Step 4: Season with salt and reduce heat to low, add a ladle of hot stock and stir until absorbed. Continue adding the stock one ladleful at a time, stirring until each has been absorbed and you've used the whole amount. When the rice is cooked, remove the pan from the heat and stir in the Parmigiano Reggiano.
Step 5: Heat the remaining amount of butter in a large, shallow, wide-based saucepan. When the butter starts to colour and smell nutty add the olive oil and the mushrooms. Cook the mushrooms until golden and tender, then add the remaining amount of Verjuice. Remove from pan.
Step 6: To serve, place the risotto on a large dish and top with the mushrooms and flat leaf parsley before drizzling with Extra Virgin Olive Oil.