Preheat the oven to 350 degrees F. Lightly spray a 9-inch square baking dish with nonstick cooking spray.
Whisk together the butter with the brown sugar and molasses in a bowl. Whisk in the eggs, half-and-half and vanilla until smooth. Stir in the salt, spices, orange zest and juice. Fold in the sweet potatoes. Pour the mixture into the prepared baking dish, then smooth the top and cover with foil.
Bake until the center is set and the potatoes are soft, about 40 minutes. Remove the foil and bake until bubbling and starting to brown on the edges, another 10 minutes. Remove from the oven and allow to cool to room temperature. Serve chilled or at room temperature with the Eggnog Whipped Cream.
Eggnog Whipped Cream:
Add the whipping cream, confectioners' sugar and nutmeg to the chilled bowl of a stand mixer fitted with the whisk attachment (or a chilled large bowl if using a hand mixer) and whisk on high speed until soft peaks form, about 2 minutes. Fold in the eggnog.