Preheat the oven to 185C / 365F.
Add the peeled and cubed apples into a bowl filled with water, reserve.
Add all the ingredients for the crumbling pastry into a bowl, mix it gently until it becomes lumpy. Reserve it.
Add all the ingredients for the filling to another bowl, mix well and reserve it.
Grease a baking dish, add one layer of the crumbles, do not stress it, add all the cinnamon and sugar apples, finish with a layer of the crumbles.
Put it in the oven and bake it for 35 to 45 minutes.
Make the custard:
Add all the ingredients for the vanilla custard to a saucepan, mix well, turn the heat to medium-low and stir until the sauce thickens up.
Transfer the vanilla custard to a small jar and serve it, either hot or cold, on top of the crumble.