Line an 8x8-inch square pan with parchment paper, leaving some overhang on the sides to easily lift the fudge out later.
In a medium mixing bowl, combine 1 cup pumpkin puree, 1 cup creamy peanut butter, 1/2 cup honey or maple syrup, and 2 teaspoons vanilla extract. Stir until smooth and fully incorporated.
Add 1/2 teaspoon cinnamon, 1/4 teaspoon nutmeg, and 1/4 teaspoon salt to the mixture. Mix well to evenly distribute the spices.
Gradually stir in 2 cups powdered sugar, mixing continuously until the mixture thickens to a smooth, fudge-like consistency.
If using, fold in 1/2 cup chopped nuts gently to add crunch.
Pour the mixture into the prepared pan and spread evenly with a spatula, pressing lightly to smooth the top.
Refrigerate the pan for at least 2 hours, or until the fudge is firm to the touch.
Lift the fudge out using the parchment paper overhang, cut into small squares, and serve. Store leftovers in an airtight container in the refrigerator.
