Prepare the Butternut Squash:
Cut both ends off the butternut squash and peel it with a vegetable peeler. Scoop out the seeds and cut the squash into cubes.
Bring 1 inch of water to a boil in a large saucepan or wok. Place the squash in a bamboo steamer, cover, and steam for 12-15 minutes or until fork-tender. Set aside.
Sauté the Mushrooms:
Heat 2 tablespoons of olive oil in a large pan over medium-high heat. Add the mushrooms and sauté until golden brown. Season with salt and pepper, remove from the heat, and set aside.
Cook the Vegetables:
Using the same pan, heat the remaining 1 tablespoon of olive oil over medium heat. Add the chopped celery, diced onion, and dried thyme. Sauté for 2-3 minutes until softened.
Stir in the minced garlic and cook until fragrant, about 1 minute.
Cook the Risotto:
Add the Arborio rice to the pan and stir constantly for about 1 minute. Gradually add 2 cups of the heated vegetable stock, stirring frequently until the liquid is absorbed.
Continue adding the remaining stock 1 cup at a time, stirring frequently until the rice is tender and creamy, about 35-40 minutes in total.
Prepare the Butternut Squash Puree:
In a blender, combine the steamed butternut squash with ½ cup of grated Parmesan cheese. Blend until smooth and creamy.
Combine:
Pour the butternut squash puree into the cooked risotto and mix well. Add half of the sautéed mushrooms and stir to combine. Adjust the seasoning with salt and pepper to taste.
Serve:
Spoon the risotto onto serving plates, top with the remaining sautéed mushrooms, and sprinkle with extra Parmesan. Serve immediately and enjoy!