Use plain pumpkin puree, not pumpkin pie mix, to control sweetness and spice., Grease the pan well for easier serving., Test cake doneness starting at 23 minutes with a toothpick; goal is moist crumbs, not raw batter., Allow the cake to cool 10 minutes before poking holes to avoid tearing and allow better soak., Pour sweetened condensed milk slowly and evenly to soak properly., Chill for at least 3–4 hours or overnight for best flavor and texture., Add Heath bits just before serving for extra crunch., If the cake starts browning too much before fully baked, cover loosely with foil for last few minutes., Variations include substituting spice or butter cake mix, adding pumpkin pie spice, using nuts instead of toffee bits, or swapping caramel sauce for dulce de leche or butterscotch sauce., For a fresher topping, use stabilized homemade whipped cream instead of Cool Whip., Store covered in the fridge up to 3–4 days., Freeze baked cake layer (no toppings) up to 2 months; do not freeze after adding Cool Whip topping.