1 large butternut squash, peeled, seeded, and cut into cubes
1 large carrot, peeled and cut into 1-inch chunks
2 tablespoons extra-virgin olive oil
7 tablespoons unsalted butter, divided (see note)
6 medium cloves garlic, minced
4 cups chicken stock
1 bay leaf
Kosher salt and freshly ground black pepper
3/4 cup heavy whipping cream
1/4 cup sour cream
Pinch ground cinnamon
1. Preheat oven to 425°F. Toss squash and carrot with olive oil and arrange on 2 rimmed baking sheets. Roast until squash and carrot are very well browned on a couple of sides, about 40 minutes. Set aside.
2. In a large saucepan, cook 2 tablespoons butter over medium-high heat until just starting to brown. Add garlic, lower heat to medium, and cook, stirring, until soft and lightly golden, about 10 minutes.
3. Add squash and carrot to saucepan and remove from heat. Pour 1/2 cup stock into each baking sheet and scrape up any browned bits, then pour into saucepan. Add remaining stock, thyme sprigs, and bay leaf and return to medium-high heat. Bring to a simmer, then lower heat and simmer until vegetables are very soft, about 10 minutes.
4. Using a blender, blend soup until completely smooth. Season with salt and pepper. Return soup to saucepan and thin, if necessary, with additional stock until desired consistency is reached. Keep warm.
5. Meanwhile, whisk cream and sour cream with cinnamon, nutmeg, and a pinch of salt, until stiff. Set aside.
6. Ladle soup into warmed bowls, spoon dollops of spiced whipped cream into each one, and top with frizzled sage, if using. Serve right away.