AT HOME (UP TO 1 DAY AHEAD)
Preheat oven to 350°. Prick cut side of potatoes with a fork in a few places. Rub potatoes all over with oil and put on a baking sheet, cut side down. Roast potatoes until tender when pierced with a fork, about 45 minutes. Let cool until you can handle them easily, about 15 minutes (keep oven on).
Meanwhile, cook bacon in a large frying pan over medium-high heat, stirring often, until very crisp, 5 to 8 minutes, depending on thickness of bacon. Drain on a paper towel. Roughly chop half the bacon.
Scoop sweet-potato flesh out of skins and into a bowl (reserve skins). Smash flesh with a fork until smooth. Add chopped bacon, half the goat cheese, milk, salt, pepper, and 1 tbsp. maple syrup, and stir just until blended. Spoon into reserved sweet-potato skins, dividing evenly and using all of it. Chill.
AT THE PARTY
Bake until potatoes are warm in the center, 15 to 20 minutes. Sprinkle tops of potatoes with unchopped bacon, crumbles of remaining goat cheese, drizzles of remaining maple syrup, and chives.