Great comfort food. Best to make fresh but you can prepare the apples well ahead of time and just refrigerate until ready to bake. They'll brown up a little bit from exposure to air but that won't matter once they're cooked, all bubbly, brown and delicious.
Wash and dry apples. Cut the apples in half and remove the core but leave any stems intact. Place apples in baking dish. Divide butter among each core cavity. Top each apple half with a tablespoon of sugar and dash with cinnamon.
Bake apples until the flesh is tender and they're bubbly and perfect looking, about 30 minutes. Serve with Creamy Custard Sauce.
Creamy Custard Sauce:
Heat the melted ice cream in a small saucepan over low heat until hot. Meanwhile, put the yolks in a mixing bowl and whisk until smooth. While whisking, slowly drizzle about 1 or 2 tablespoons hot melted ice cream into the yolks until blended. While whisking constantly, slowly add the rest of the hot liquid to the yolk mixture. Pour the mixture back into the saucepan and return to low heat.