Begin by preheating your oven to 425°F (220°C). In my early trials, I roasted the squash at a lower temperature, which resulted in less caramelization. The higher heat here is crucial for drawing out the natural sugars and enhancing the squash's flavor.

On a large baking sheet, toss the cubed butternut squash and pears with 2 tablespoons of olive oil, cinnamon, nutmeg, salt, and pepper. Spread them in a single layer to ensure even roasting. I've found that crowding the pan steams the ingredients rather than roasting them, which can mute their flavors.

Roast in the preheated oven for about 25 minutes, or until the edges of the squash begin to brown and the pears are tender. It's tempting to stir them frequently, but I've learned that letting them be allows for those desirable caramelized bits to form.

While the squash and pears are roasting, heat the remaining tablespoon of olive oil in a large pot over medium heat. Add the diced onion and sauté until translucent, about 5 minutes. I remember the first time I rushed this step and the onions were slightly raw, which resulted in a less harmonious blend of flavors.

Add the minced garlic and cook for another minute until aromatic. It's crucial not to let the garlic brown, as it can become bitter and overpower the delicate sweetness of the other ingredients.

Pour in the vegetable stock and bring to a gentle simmer. Add the roasted squash and pears to the pot, and let the mixture simmer for about 15 minutes. This step allows the flavors to meld and deepen, creating a more cohesive soup.

In a small saucepan, gently heat the heavy cream with the tablespoon of fresh thyme leaves. Once small bubbles begin to form around the edges, remove from heat and let it steep while the soup simmers. This infuses the cream with a subtle, earthy flavor that complements the sweetness of the squash and pears beautifully.

After the soup has simmered, remove the thyme sprigs from the cream and discard. Using an immersion blender, purée the soup directly in the pot until smooth. I've learned that blending the soup while it's still hot creates a silkier texture, as the heat helps to emulsify the ingredients.

Stir in the thyme-infused cream and season the soup with additional salt and pepper to taste. It's important to season at this stage, as the flavors will have developed and you can better gauge the seasoning needed.

Ladle the soup into bowls and garnish with a drizzle of the thyme-infused cream and a few fresh thyme leaves. A dear friend, who's a chef, once suggested this final touch, and it's been my go-to ever since, adding both visual appeal and a burst of flavor.