In a 3-qt. sauce pan, bring the chicken stock to a simmer over medium heat. Cover and reduce the heat to low.
Preheat a chef's pan over medium heat until the rim of the pan is hot to the touch. Add the olive oil and heat for an additional minute. Add the butternut squash and half of the onions and cook until the squash is tender, about 7 minutes. Stir in the wine, nutmeg, herbes de Provence and salt and cook, stirring occasionally, until most of the liquid has evaporated, about 12 minutes.
Remove from the heat and cool slightly. Puree the mixture in a blender or food processor until smooth and reserve.
Return the pan to the burner and heat over medium heat until the rim is hot to the touch. Add half of the butter. When the butter is bubbling, add the rice and remaining onions and sauté until the onions are translucent, about 7 minutes.
Add a cup of hot stock to the pan and begin to stir with a wooded spoon. Stir constantly until the liquid has been absorbed. Reduce the heat to low. Gradually add three more cups of the hot stock, one ladle full at a time, stirring constantly and waiting until the stock has been absorbed before adding another ladle full.
Stir in the squash puree. Continue cooking and adding 3 more cups of stock to the pan, one ladle full at a time, stirring constantly and waiting until the stock has been absorbed before adding another ladle full. Cook until the rice is tender, about 10 minutes longer.
Stir in the parsley, remaining butter and parmesan cheese. Serve immediately.