Preheat the oven to 180 degrees Celsius on the bottom oven cut the apple up into small thin pieces and lay them at the bottom of a ovenproof container
Pour the caster sugar over the apple and take 3 tablespoons of water and put over the top
Now for the topping take the plain flour and butter and mix together until it resembles fine breadcrumbs
Add the oats to the mixture and carry on doing the same thing for a few minutes and then add the brown sugar and mix into the mixture
Pour the mixture over the apples and level out put into the oven for 25 minutes