Soak the raisins in the Grand Marnier for 5 minutes, then drain.
In a frying pan, caramelise the apples with the brown sugar and cinnamon in a little butter until golden brown, about 3 minutes. Stir in the almonds and raisins and cook for a further minute, coating everything in the caramel. Remove from the heat and allow to cool for a few minutes.
Lay out the filo pastry, brushing each sheet with butter and dusting with a little icing sugar before layering 3 or 4 on top of each other.
Spoon the apple filling in a line down the middle of the pastry, then fold in each of the opposite sides to form a long parcel.
Brush the top with butter and dust with a little caster sugar. Bake in the oven for 7-8 minutes for 200C.
Whip the cream until thick and serve the strudel fresh from the oven with the cream drizzled over and a dusting of icing sugar.
