Preheat your oven to 200°C/180°C(fan)/400°F/Gas 6.
Peel and chop 800 g Apple. Put them into a large baking dish along with 300 g blackberries.
Add 170 g Light brown sugar and mix everything together.
In a mixing bowl, add 200 g Plain flour and 170 g Butter. Using your fingers, combine to make a breadcrumb consistency, leaving a few lumpy bits.
Add 120 g Oats and 50 g Caster sugar and mix well.
Spread the crumble mixture over the top of the fruit.
Put in the preheated oven for 40 minutes.
Notes
Make sure the apples are cut very small. The apples aren't softened before they go in the oven, so if you want them nice and soft they need to be chopped up small. If you wanted them to have more bite to them, then you can keep them larger.
Don't worry if the apples start going brown. This happens when cut and they get air to them and it will not change the flavour. You can soak them in water with a little lemon juice if you want to stop this from happening whilst you are preparing your other ingredients though.
Feel free to adjust the amount of sugar used depending on how sweet you like your crumble.
Cooking times will vary depending on your oven. So your crumble may cook quicker, or take a little longer to cook. You will know it is cooked when it is starting to brown on top and you can see the fruit juices bubbling at the side.
Allow the crumble to cool a little before serving (only a few minutes), as it will make it easier to scoop out without falling apart. But, it is called crumble for a reason!
Add a pinch of cinnamon to the crumble topping for more autumnal flavour.