Butter a 9-by-13-inch baking pan and set it aside.
In a heavy saucepan, mix the sugar, butter, evaporated milk, pumpkin, and pumpkin pie spice.
Gradually bring the mixture to a boil, continually stirring it with a wooden spoon. Continue stirring and boiling it over medium heat until the mixture reaches 236 degrees on a candy thermometer (about 11 minutes).
Immediately remove the saucepan from the heat. Stir in both the white chocolate and cinnamon chips. Once the chips are blended in, add the marshmallow creme and vanilla. Mix until well combined. The mixture should be creamy. Stir in nuts if desired.
Immediately pour the creamy mixture into the prepared baking pan. Spread it evenly. Let it cool at room temperature.
Once the mixture has cooled, remove it from the pan and cut it into squares. Store the fudge in the refrigerator in an airtight container.
A candy thermometer will help you know if your mixture has reached the right temperature. If you don't own a candy thermometer, you can use the cold water test. Carefully drop a spoonful of the hot sugar syrup into cold water. If the syrup forms a soft ball, then your mixture is ready to be taken off the heat.