Creamy Squash and Mushroom Risotto

Ingredients

In a pot, bring stock to a simmer.
In a heavy-based saucepan, heat 1 tablespoon of oil over medium heat and add onions and thyme. Cook for a few minutes until soft, but not coloured.
Turn heat up, and add mushrooms. Do not crowd the pan, and cook in batches if necessary.
Cook until mushrooms are brown. Deglaze pan with wine (if using). Remove and set aside.
Add 1 tablespoon of butter. When foaming, add rice and stir to toast for 1-2 minutes.
When rice is translucent, add a ladle of stock and squash to pan. Stir once to submerge rice and let sit until stock has absorbed. Adjust heat so rice and stock are at a gentle simmer. When absorbed, continue to add stock a ladle or two at a time, stirring once each time.
If making ahead, stop when rice is about 75% cooked. The outside of the grains will have begun to soften, but will be chalky inside. Spread rice out on a baking sheet to cool rapidly. Refrigerate until ready to cook.
When ready to cook, add rice mixture, mushrooms, and a couple ladles of stock to a pan over medium heat.
Stir rapidly while agitating the pan. Add butter and continue to stir and add stock until desired consistency is reached and rice is cooked through. Texture should be creamy, not too thick and give some movement on the plate.
Remove from the heat and stir through half the parmesan cheese, lemon zest, and juice. Season to taste and sprinkle with remaining cheese and a drizzle of olive oil.