Grease or line an 8x8 baking dish with parchment paper or foil, and set aside.
In a medium saucepan, combine the sugar, evaporated milk, corn syrup, pumpkin and spice over medium heat.
Cook, stirring occasionally. The mixture will come to a boil - just keep an eye on it and reduce the heat if it boils up close to the top of the pot.
Continue cooking until mixture reaches soft ball stage (235-245 degrees). This took me between 30 and 45 minutes. When it reaches this stage, remove from heat.
Add the butter - do not stir at this point - and allow to cool to room temperature. Once it reaches room temperature, stir, stir, stir until it loses it's sheen and starts to stiffen.
Then IMMEDIATELY push into your prepared baking dish, smooth out the top, and allow to cool completely before cutting. You can score the tops so that it makes for easier cutting once cooled, but it's not necessary.