To make the sponge, add the soft butter and sugar to a large mixing bowl, and use a hand mixer to cream them together until you have a pale yellow colour and creamy texture.
Add the eggs one by one, beaten well after each egg added.
Add the vanilla extract, milk and sifted flour, and use a silicone spatula to mix all the ingredients together.
Grease and flour a 23 cm / 9 inch round cake tin, and spoon the batter in one even layer.
Peel and chop the apples into small cubes, and add them to a dish together with the light brown sugar, mixed spice and cornflour.
Mix to coat the apples well, then top the sponge with an even layer of apples.
Scatter the blackberries over.
To make the crumble topping, mix together the flour, oats, mixed spice and sugar.
Add the melted butter and mix again to get a crumbly texture.
Scatter the mixture all over the fruit and bake in the preheated oven at 180 degrees Celsius (350 Fahrenheit) for 60 minutes or until a skewer inserted in the middle comes out clean.
Remove the cake from the oven and allow to cool down completely.
Drizzle the cake with caramel and enjoy!