• Preheat oven to 170c fan-forced/190c conventional/375f.

Apple filling

• First peel the apples - you can place them into a bowl of water as you go to help prevent browning.
• Cut the apples into smallish pieces, roughly the size of your thumb-tip. You don't want them too small as they will cook too quickly and break down.
• Place the apples directly into your baking dish and toss with the sugar, vanilla and lemon juice and set aside.
You can also use green Granny Smith apples, though as they are less sweet/more tart I'd consider increasing the amount of sugar in the filling to 50g.

Crumble topping

• Combine all of the dry ingredients together in a bowl, then add the cold cubes of butter.
• Using a light touch and your fingertips, rub the butter and flour mixture together to form the crumble, until you have a mix that resembles coarse breadcrumbs, with some larger pieces remaining.
• Cover the apples with the crumble topping and bake in the centre of your oven for 40-45 minutes, until the apples are bubbling out of the corners and you can see they're nicely caramelised. The crumble topping should be lovely and golden.
• Allow to rest for 10 minutes before serving.
Serve with ice cream, cream, or custard - no judgement here whichever way you prefer!