Place a large oven-safe cast iron pan on the stove and heat 1 tablespoon of oil. Add the chicken and brown in batches, being careful not to overcrowd the pan. Once the chicken is brown (not cooked through), remove from the pan and set aside.
Add the butter and sliced mushrooms to the pan and cook down until browned and reduced by about half the size. Remove and set aside.
Add the remaining oil to the pan and add in the chopped shallots and garlic. Use a wooden spoon to ensure the shallots and garlic do not stick to the bottom of the pan. As they start to brown use the wooden spoon to break apart the shallots as they soften.
Once the shallots have softened, add in the arborio rice and stir through for a couple of minutes until shiny.
Add in the stock and white wine, stir through and bring to the boil. Preheat the oven to 180°C.
Once boiling, add the chicken and mushroom back into the pan and stir to combine, ensuring that the chicken is completely submerged.
Cover and place into the preheated oven and bake for 25-30 minutes or until there is no liquid remaining and the rice is soft and tender.
Stir through the parmesan cheese if using and season with salt and pepper to taste. Serve with a generous squeeze of lemon and a sprinkle of fresh parsley.