Pat chicken dry with kitchen paper. Season well with salt, lots of black pepper, and 1 tsp lemon zest. Rest 30 minutes (or cover and refrigerate overnight).
While the chicken is getting some flavor, wash, peel, slice, dice and mince the shallot (or onion)), leeks, mushrooms and garlic. Zest the lemon and grate the Parmesan, so everything is ready when you need it.
Heat a large frying pan on medium-high. Add 2 tbsp olive oil and sear chicken around 3 minutes per side until golden.
Preheat oven to 190°C. Transfer chicken to a tray and bake 25 minutes. Set it aside to rest.
In the same pan, sauté shallot on medium heat 2 to 3 minutes until translucent.
Add mushrooms and sauté 10 minutes.
Add minced garlic 30 seconds to 1 minute. Add leeks and sauté gently 5 minutes until they wilt slightly (add a splash of hot water if the pan is too dry).
Add the remaining 1 tbsp olive oil, add rice, and stir to coat. Optional: add a splash of wine and let it absorb.
Add hot stock one ladle at a time and stir continuously. Cook for about 30-40 minutes for a very soft consistency, until stock is used up. Start tasting after 20 to 25 minutes and stop when you like the bite.
Finish with lemon juice to taste and add the grated Parmesan. Adjust seasoning with salt and pepper to taste.
Slice chicken and serve on top, or dice and fold through. Serve immediately while hot and very creamy.