Place apples in a large pot with enough water to cover, and bring to a boil. Reduce heat to low, and simmer 15 minutes, or until soft. Drain, and cool. Place in a large bowl, and toss with 2 tablespoons sugar to evenly coat.

In a large bowl, whip together the 1/2 cup butter and 2 tablespoons sugar until fluffy. Mix in the egg. In a separate bowl, mix 2 cups flour, baking powder, and custard powder. Mix dry ingredients into the bowl with butter and sugar. Press crust into the bottom and up the sides of a 9 inch springform pan.

Preheat oven to 400 degrees F (200 degrees C).

Drain apples and place into the crust. Cut together 3/4 cup sugar, 3/4 cup butter, 1 1/4 cups flour, and cinnamon. Mix in coconut and oats. Sprinkle over the apples.

Bake 1 hour in the preheated oven, until golden brown. Remove sides from pan and allow crumble to cool before serving.