Preheat the oven to 180˚C/Gas Mark 4. Butter an ovenproof dish such as a deep pie dish. Place the apples in the dish and add the cinnamon and maple sugar or caster sugar. Pour over the maple syrup, cover with foil and bake for 20-25 minutes, until the apples have softened slightly.
Sift the flour, cinnamon, nutmeg and baking powder into a bowl then add the sugar. In another bowl, beat the egg with the milk and vanilla extract slowly add this to the flour mixture, stirring all the time but being careful not to overheat. Add the maple syrup and keep stirring to form a batter-like mixture. Fold in the butter.
Pour the batter over the apples, ensuring it covers them completely and return the dish to the oven. Cook, uncovered for 20-25 minutes, until, the topping is golden and firm. Dust with icing sugar and serve warm, with whipped cream or yoghurt.
Preparation time approximately 90 minutes.