Sift the flour, baking powder and bicarbonate of soda in a large bowl. Add sugar, 1 tsp of grated nutmeg and cinnamon powder to the flour mixture and mix it well.
Make a well in the middle, add egg, milk and melted butter to the flour mixture and stir to combine. Do not over mix it. (The mixture should be quite lumpy. If the mixture is too thick like a dough, add a tbsp of milk to loosen the mixture.) The mixture should be similar to that of a thick batter consistency.
Preheat the oven to 180 degree Celsius.
Line the muffin tray with muffin cups. Spoon half of the mixture equally in the 6 muffin cups. Using the back of a spoon, make a small well in the middle of the mixture, drop a teaspoon of custard and a teaspoon of apple filling in the well. Top with the remaining muffin mixture and sprinkle with brown sugar and grated nutmeg on top.
Bake it in the preheated oven for 25 to 30 minutes.
Stand in the pan for 5 minutes before turning to a wire rack. Serve warm.
For Apple Filling:
Peel and slice the apples thinly in small size.
Mix the apple, sugar, cinnamon powder and lemon juice in a bowl. Let it rest in a bowl for 30 minutes. After 30 minutes extract all the juice released from apples.
Add the extract, corn-starch and butter in a pan, let it boil. When it starts boiling, add the apples and cover it cook till it looks thick and saucy.
Remove it from heat, let it cool down completely and use it for the recipe.