Preheat the oven to 200 C / Gas 6. With a small, sharp knife cut a cross in each of the chestnuts. Lay on a baking tray.
Bake for 20 to 30 minutes until the inner nut is tender and the shell is peeling away at the cross. Remove from the oven and peel. Discard the shell and finely chop the chestnuts.
In a saucepan over a medium heat, melt the butter and stir in the brown sugar until dissolved. Add the digestives, raisins and chestnuts. Stir well then remove from the heat and set aside.
Reduce the oven temperature to 150 C / Gas 2.
For the apples:
Core the apples then scrape out a little more of the centre so that there is a good size cavity in the apple. Rub the apple with butter then divide the filling equally among the apples and press in to fill. On top of each apple lay a slice of orange, followed by a slice of lemon topped with a star anise. Secure the fruit on the apples with the skewer if necessary. Dust with a little cinnamon and nutmeg. Transfer to a greased baking dish then cover with foil.
Bake in the oven for 40 minutes then remove the foil and cook for a further 15 minutes until the apples are soft yet still holding their shape.
Remove from the oven and serve with vanilla ice cream.