Pour the broth into a 4qt sauce pan on a burner next to the one you will be cooking the risotto on. Heat until steaming but not simmering, keep on low heat.
Wash leeks well to get rid of any sand or grit. Quarter lengthwise then finely slice. Core the apples then peel and dice into small pieces - less than half an inch ( less than a centimeter).
Heat the oil and butter in a large heavy bottomed pan ( enamel cast iron are great for risotto) and add the leeks and apples. Cook for 20 minutes over medium heat, stirring occasionally until the leeks are caramelized and the apples are very soft.
Add in the thyme, garlic and lemon juice, salt, pepper and nutmeg and sauté for one minute. Next, add in the rice and wine ( or brandy if using) and stir, cook until the wine has been absorbed.
Add in two cups of the warm broth and stir. Let the rice cook for a few minutes to start absorbing the liquid before stirring again, stir until it is almost absorbed then ladle in half a cup of broth and repeat the process. It takes about 5 minutes per ladling of broth, stirring, letting it absorb some then stirring some more before adding more broth. When around 6 cups of the broth has been added in, taste the rice and see how the consistency is to your liking. It should be cooked but still have “bite” to it. Al dente like pasta. You can add all the liquid if you like a thinner consistency to your risotto or add only around 6 cups if you like it thicker.
Once the rice consistency is to your liking, taste and add more salt, pepper or nutmeg if you like. Remove from the heat and add in the brie and parmesan. Stir until the cheese has melted in, you might still have small pieces of brie, that is ok. Keep warm until ready to serve. Risotto is best served immediately after cooking.
Spoon the risotto into bowls and garnish with fresh, diced apple, a sprinkling of parmesan, some chopped, toasted walnuts and some more fresh thyme. You can serve it with a square of brie cheese on the top as well if you like.