Preheat the oven to 400 degrees .
Brush the cut sides of the squash with oil; season with salt, pepper and nutmeg. Place on a baking sheet and roast until tender, 35 to 40 minutes. Let cool. Scrape the roasted squash flesh into a food processor and puree.
Scatter the baguette slices on a large baking sheet; toast on both sides. Rub the toasts with the cut sides of the garlic, drizzle or brush with olive oil and season with flaky sea salt, if using.
In a small skillet, melt the butter over medium heat. When the foam subsides, add the sage leaves and cook until crisp. Remove the sage leaves and add the browned butter to the squash puree. Stir in the Parm and half the sage. Taste and adjust the seasonings. Transfer to a bowl and garnish with the remaining sage. Serve with the toasts.