Six pumpkin cake layers with toasted marshmallow filling, pumpkin pie filling, shortbread crumbs and vanilla buttercream.
Preheat 350 degrees F. Spray three 8-inch or four 6-inch round cake pans with cooking spray and line the bottoms with parchment paper rounds. Spray again and set aside.
Pour the mixture into the pan and bake for 50 to 55 minutes or until filling has puffed at the edges and center is almost set. Let cool completely and then move to an airtight container, mix, and then store in fridge overnight.
Combine the salt and flour into a large bowl. Stir to combine. Pour in the melted butter and water. Stir to combine, until you get small clumps.
Frost the cake with the remaining buttercream.