Preheat the oven to 400 degrees. Lightly butter a rimmed baking sheet.

Place the squash halves, cut side down, on the prepared baking sheet. Bake until the squash is easily pierced with a fork, 40-50 minutes. Let cool slightly, then scoop out the flesh, discarding the peel, and transfer to a large bowl. Add the orange juice, half-and-half, nutmeg, and 2 tablespoons of the butter. Season to taste with salt and pepper. Mash with a potato masher or beat with an electric mixer until blended and smooth. Transfer to a warmed serving bowl.

Just before serving, in a small saucepan over medium high heat, melt the remaining 4 tablespoons (2 oz) butter and cook until it turns golden brown, about 3 minutes. Drizzle the butter over the squash. Serve hot.