Line the baking pan with parchment paper, allowing some overhang for easy removal.

In a medium saucepan, mix together the sugar, butter, and pumpkin puree over medium heat. Stir until the butter is melted.

Stir in the vanilla extract, cinnamon, nutmeg, and salt.

Allow the mixture to come to a gentle boil, stirring constantly.

Cook for about 8 to 10 minutes, or until it reaches the soft ball stage (around 238°F on a candy thermometer).

Remove from heat and immediately stir in the white chocolate chips until fully melted.

Fold in the chopped nuts, if desired.

Pour the mixture into the prepared pan and spread it evenly. Let it cool at room temperature for at least two hours before cutting into squares.