Add the butternut squash, ½ cup vegetable broth, milk and 2 cloves peeled garlic to a large pot over high heat and bring to a boil.
Reduce heat to medium and cook until the squash is fork tender, app. 20 minutes.
In the meantime, bring the additional 8 cups of vegetable broth to a boil in a large pot.
In a separate large skillet over medium heat, melt the butter.
Once the butter is melted, add the diced onion, saute 3-5 minutes, then add the remaining 2 cloves of garlic, minced, saute 1-2 minutes then add the rice.
Toast the rice in the skillet for 2-3 minutes, then begin adding the boiling vegetable broth to the rice 1 cup at a time.
Once the first cup of broth is absorbed into the rice, add the next cup and stir the risotto.
Continue this process until all of the broth has been absorbed and the risotto is nice and creamy.
Stir the parmesan cheese into the risotto.
At this point the butternut squash should be finished cooking.
Add the nutmeg, salt and pepper to the squash with the milk, vegetable broth and garlic, pour all of the above into a blender or food processor and puree.
Add the pureed squash to the risotto and stir to combine.
Reduce the heat on the stove to low and simmer 5-10 minutes, or until the pureed squash has been absorbed into the risotto.
Make ahead: The butternut squash puree can be made ahead of time and stored in the refrigerator for 1-2 days. I do not recommend making the risotto ahead of time, as it will not keep the same consistency.
Broth: I use vegetable broth to make this recipe vegetarian, but chicken broth or stock can be used in its place.
Rice: It is important to use arborio rice in this dish to get the desired texture. Do not rinse the rice ahead of time, this will rinse off some of the starch that helps make the risotto so creamy!
Instant Pot: refer to the post above for instructions on how to make the risotto in an instant pot.