Preheat oven to 350 degrees F. Make the custard mixture by mixing the spices into the pumpkin and then mixing it with the eggs, milk, vanilla, and maple syrup. Whisk until smooth and combined.

Make the brown sugar topping by mixing the topping ingredients together until it is crumbly.

In a greased baking dish (9x13 or slightly larger; mine was larger), put a single layer of 8 bread slices. Pour about 1/3rd of the custard over the bread and use a spatula to spread the mixture and soak the bread.

In the opposite direction, layer the remaining 8 bread slices on top, slightly overlapping each other if needed. Pour the remaining custard on top and around the edges, filling in the gaps. Sprinkle the topping over top.

Bake the casserole for 35-45 minutes or until golden brown and the egg custard is set and firm. If your topping has melted, take a knife and spread it evenly on the top pieces of toast. If the topping holds shape, you can leave it as is (this will depend on which type of sweetener you use). Allow to rest a few minutes to set up.