For the pastry, combine the cake flour, rye flour, icing sugar and salt in a processor. Pulse to aerate the flour. Add the butter and pulse until the texture is roughly crumbed. Add the water and pulse until the dough comes together. Turn out and press together lightly. Wrap in cling film and chill for 1 hour.

Preheat the oven to 200°C. Place the oven rack on the lowest rung.

Divide the dough in half. On a floured board, roll each piece out to a 3mm thickness. Line a Le Creuset Classic Square Dish on the base and sides. Chill for 10 minutes.

In a large mixing bowl, whisk together the demerara sugar, cornflour, cinnamon, nutmeg, brandy, and cream. Add the apples and toss to coat.

Add the apples and juices into the pastry case. Scatter over the cubed butter and cover with the remaining pastry, either plaiting 2.5cm strips of pastry or a full pastry sheet. Trim the overhanging edges and pinch together to seal. Brush with egg wash and scatter over the demerara sugar. Cut three small steam slits on top if the pastry is a full sheet. Bake for 15 minutes on the lower shelf. Reduce the temperature to 180°C, move the shelf to the middle rung and bake for a further 60-65 minutes. Cover with foil for the last 15-20 minutes to prevent over-browning.

Cool on a wire rack for 10 minutes. Serve with butterscotch sauce and vanilla bean ice cream.

For the butterscotch sauce, melt the butter in a saucepan over a medium heat. Add the sugar and cook until the mixture is a deep caramel colour, about 5-6 minutes. Pour in the cream and simmer until thickened, about 8-10 minutes. Stir in the vanilla and salt.