Preheat oven to 350°F. Coat a 9x12-inch baking dish with nonstick spray and set aside.
Combine the pumpkin puree, evaporated milk, eggs, sugar, and pumpkin pie spice in a large mixing bowl. Stir to combine and pour into your prepared dish.
Sprinkle a whole box of dry cake mix evenly over the pumpkin layer, followed by your crushed graham crackers.
Spread sliced butter pieces all over the cake mix making sure to cover as much of the dry mix as possible.
Bake in the preheated oven for 45-50 minutes until the center is set and the edges are lightly browned.
Serve warm or at room temperature. Top with ice cream, caramel sauce and toffee bits.