Pour lukewarm milk over the brioche slices. Brush a quiche dish with butter and layer the brioche slices like a roof tile. Spread the apples evenly in between.
Mix the remaining milk with the beaten eggs, sugar to taste, cinnamon and whipped cream and pour over the top. Bake in a heated oven at 160 °C for at least 1 hour. Later sprinkle with brown sugar and butter flakes and brown briefly under the broiler.
Serve with vanilla sauce, vanilla ice cream or whipped cream.