Line the bottom and sides of a 9 x 13-inch baking pan with aluminum foil and prepare with nonstick cooking spray; set aside.

In a medium heavy-bottomed saucepan over medium heat, combine the sugar, brown sugar, butter, milk, pumpkin, and pumpkin pie spice. Bring to a full rolling boil, stirring constantly. Continue boiling, stirring constantly, until a candy thermometer reaches the soft-ball stage, 234 degrees, 10–12 minutes.

Remove from heat and quickly stir in the chocolate chips, marshmallow creme, and vanilla. Stir until chocolate is completely melted, and immediately pour the mixture into the prepared pan. Cool the pan to room temperature on a wire rack, and then cover and chill in the refrigerator for 3 hours. Remove the foil from the pan, and cut the fudge into 1-inch squares.