Heat oven to 375℉/190℃.
Cut squash in half lengthwise.
Scoop out seeds and pulp.
Place skin side down on sheet pan.
Brush cut sides with olive oil.
Season with salt and pepper.
Bake until tender, 35-40 minutes.
When cool, peel and cube squash.
Purée 2 cups squash with vegetable broth and herbs. Set aside.
In an 8-quart stock pot, melt butter.
Add onion.
Sauté over medium heat until translucent, 3-4 minutes.
Add risotto.
Cook and stir until rice starts to color, 1-2 minutes.
Add garlic and wine.
Cook and stir 1-2 minutes, or until wine is absorbed.
Add broth, one ladle at a time, cooking and stirring until broth is absorbed each time.
Add remaining butternut squash with last ladle of broth.
Stir in parmesan.
Season to taste with salt and pepper.