Preheat the oven to 180C/350F and spray an 11x9 inch pan with cooking spray. An 11x7 pan will work too, but you may need to cook it a few minutes longer.
Make the filling first: Place the pumpkin, spices, salt and sugar into a large bowl and mix until well combined. Add in the sliced apples and stir until all the apple slices are coated in pumpkin. Leave to one side.
Make the topping: Place the flour, sugar, salt, baking powder, egg and vanilla into a large bowl and mix until the mixture starts to come together, then add the butter, a little at a time, while stirring continuously until the mixture comes together into one sticky ball.
Tip the pumpkin apple mixture into your prepared pan and spread into an even layer. Crumble or spoon lumps of the topping over the fruit. It's fine if the topping doesn't totally cover the fruit.
Place in the oven for 32-37 minutes, until browned around the edges, bubbling and the top is firm to the touch and golden all over. Stick a fork into the centre to feel whether the apples are soft if required.
Leave to cool in the pan or at least 30 minutes before serving with custard and ice cream.
Pumpkin Apple Cobbler is best served on the day it's made, but will keep overnight in the fridge if covered. The cobbler is best served warm, so you can microwave any leftovers for 30 seconds - 1 minute to reheat.