Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.

Spread the cubed butternut squash across the baking sheet. Drizzle with 1.5 tbsp olive oil and season with 1/2 tsp kosher salt and 1/4 tsp black pepper. Drizzle remaining 1/2 tbsp olive oil over the exposed garlic head, wrap tightly in foil, and place on the sheet next to the squash.

Roast for 25 to 30 minutes, tossing halfway through, until the squash cubes are fork-tender with caramelized golden edges and the garlic cloves are deeply golden and jammy-soft.

Transfer the warm roasted butternut squash into a high-powered blender. Squeeze the soft roasted garlic cloves out of their skins directly into the blender.

Pour in 1 cup of warm vegetable broth, heavy cream, freshly grated nutmeg, and a pinch more salt. Blend on high speed for 60 to 90 seconds until completely smooth, glossy, and velvety like liquid gold. Taste and adjust seasoning if needed.

Bring a large pot of generously salted water to a rolling boil. Cook fettuccine until 1 minute shy of al dente according to package instructions. Dip a heat-proof measuring cup into the pot to reserve 1/2 cup of starchy pasta water, then drain the pasta.

While pasta cooks, melt the unsalted butter in a large deep skillet or Dutch oven over medium heat. Add the fresh sage leaves in a single layer. Fry for 2 to 3 minutes until the butter foams with nutty brown flecks and the sage leaves turn dark green and crisp. Use a fork to transfer crispy sage to a plate, leaving the browned sage butter in the skillet.

Pour the blended butternut squash purée into the skillet with the browned butter over low heat, whisking together until glossy and steaming.

Add the hot drained fettuccine and freshly grated Parmigiano-Reggiano into the sauce. Toss vigorously using tongs for 1 to 2 minutes, splashing in 2 to 4 tbsp of reserved starchy pasta water as needed to create an ultra-glossy emulsified sauce that coats every strand.

Divide among warm pasta bowls. Top with crispy fried sage leaves, toasted pine nuts, extra grated parmesan, and freshly cracked black pepper. Serve immediately.