Peel, quarter, core and finely slice apples dropping them into a pan filled with water as you prepare (to prevent browning).
Drain the apples and add 1 tablespoon water, 3 tablespoons granulated sugar and, 2 teaspoons vanilla sugar to the pan.
Bring pan to a simmer and stew apples gently under a lid until tender (about 10 - 15 minutes).
Transfer stewed apples to a bowl and allow to cool.
Whip the cream in a bowl until softly stiff, then refrigerate.
Put the oat cookies in a bowl and crush with the back of a rolling pin until you have irregular crumbs. (Using a food processor just turns them into too fine a crumb).
Spoon a layer of cooled stewed apple into 6 serving glasses/goblets or one large bowl followed by a layer of crushed cookies, then repeat and top with a layer of whipped cream and grated chocolate.
Serve straight away or chill in the fridge until serving.