The key is not in the ingredients – it’s a simple enough crumble mixture with the magic 3:2:1 ratio of flour:butter:sugar. Note, that’s the same ratio you use to make shortbread. The added oats (or almonds, if you don’t have any) is now a fairly common addition.
First, preheat your oven to 180C/160C fan/Gas 4. Look out a good crumble dish – this could be a deep pudding dish, a pie dish or even an ovenproof frying pan.
Start by preparing your crumble mix – weigh your flour into a large bowl. Weigh and cut up your butter into manageable chunks, then rub into your flour using your fingers. You want them like breadcrumbs, but it doesn’t need to be perfect.
Once the butter is rubbed in, add the sugar and oats (or almonds) to your mix and rub everything together. Now, use your hands to squish everything together. You want nearly (but not quite) all of it to come together into one big lump. You don’t want to work it so much it comes into a dough. Then set it aside.
Peel and core your apples, before slicing them into a very think slices (1-2mm). Use a layer of these to line the bottom of your pudding dish, before sprinkling with enough caster sugar to cover and a few blackberries. Add another layer of apples, sugar and blackberries until you’ve no apples or blackberries left.
Crumble your big lump of crumble mix onto your fruit – lumps are what we want, but break them up if you have to cover any bare fruit near the middle. Then, sprinkle a little bit more sugar on top.
Bake for 35-40 minutes, or until your crumble topping is golden brown and crisp. For an extra crisp topping, chuck half a small glass of water onto the side of the oven when you bake to cause the sugar on top to caramelise. Leave it for 15 minutes to cool before serving, with custard or ice cream or cream. Maybe all three.
You can make a gluten-free crumble topping easily, by replacing the flour with half-n-half porridge oats and ground almonds.