Preheat the oven to 200C/Gas 6.
After you clean your apples, cut them into quarters, removing cores and slice each piece in two. Put them into a pan and add a sprinkling of sugar. Add a tablespoon of water and cook over a medium heat for about five minutes, until the apples start to soften.
Transfer the apple mixture to a shallow ovenproof pie dish.
Blend the flour and butter in a food processor for a few seconds, until the mixture looks like breadcrumbs. You can quickly do this by hand, swiftly using the tips of your fingers so you don’t overwork and warm the butter.
Stir in the oats and the brown sugar and sprinkle over the cooked apples in the pie dish.
Transfer to the oven to bake for 30 minutes or until crisp and golden-brown on top.