Prepare Roasted Garlic White Sauce: Preheat oven to 400°F (200°C). Slice the top off the garlic head, drizzle with olive oil, wrap in foil, and roast for 40-50 minutes until soft. Squeeze roasted garlic cloves into a small bowl, mash with a fork. Whisk in heavy cream, grated Parmesan, and a pinch of nutmeg. Season with salt and pepper to taste. Set aside.