Heat the oven to 425 Fahrenheit, 220 Celsius. Gently score the apples around their equators with a knife to allow steam to escape (this prevents them from popping).
Place the apples in a 12-inch pan, smudge the soft butter all over each apple, then roll them in the brown sugar. Pour in the cider, and add the ginger, cinnamon and star anise.
Bake for about 60 minutes (depends on type and size of apple used), basting once or twice if you think of it.
When you can poke a fork to the core of the apples and detect nothing but soft sauce within, remove the pan from the oven and place it over low heat on the stove. Add the apple cider vinegar to the pan and simmer until the sauce reduces to the consistency of maple syrup, about 10 minutes.
Serve each apple in a bowl with a scoop of vanilla ice cream and pour the cider caramel over the top.