Preheat your oven to 400°F (200°C). Peel and cube the butternut squash, seasoning it with salt and pepper. Spread on a lined baking sheet and roast for 25-35 minutes until soft.

Melt butter in a large skillet over medium-high heat. Add minced onion and sauté for 3-5 minutes until translucent and fragrant.

Stir in the Arborio rice and sauté for 2-3 minutes until the rice grains are lightly toasted.

Pour in a splash of dry white wine and stir until fully absorbed by the rice, about 2-3 minutes.

Remove roasted squash from the oven, mash until smooth, and stir into the rice mixture with fresh thyme. Let flavors meld for 2 minutes over low heat.

Gradually add warm broth one cup at a time, stirring continuously until absorbed. This process should take about 20 minutes.

Taste and season with kosher salt. Stir in Parmesan cheese if using, and remove thyme sprigs. Give a final stir to combine.

Spoon risotto into warm bowls and garnish with additional grated Parmesan or herbs if desired. Serve immediately.