1 cup chopped walnuts, divided
1 1/2 cups granulated sugar
1 1/2 cups packed light brown sugar
3/4 cup (1 1/2 sticks) unsalted butter, cut into small pieces
2/3 cup (5 fl.-oz. can) evaporated milk
2/3 cup pureed pumpkin
1 teaspoon ground cinnamon
1/2 teaspoon ground ginger
1/4 teaspoon nutmeg
1/8 teaspoon cloves
1/8 teaspoon allspice
2 cups (12-oz. pkg.) white chocolate chips
1 jar (7 oz.) marshmallow crème
1 1/2 teaspoons vanilla extract
Preheat oven to 350 degrees F. Spread the nuts onto a baking sheet and place in preheated oven 5-7 minutes until fragrant. Shake the baking sheet halfway through baking so the nuts will toast evenly. Remove nuts from oven and set aside to cool completely.
Line a 13 x 9-inch baking pan with foil letting the foil extend up the two short sides of the pan and overhang slightly on both ends.
In a heavy saucepan, combine sugar, brown sugar, evaporated milk, pumpkin, butter and spice. Bring to a full rolling boil over medium heat, stirring constantly. Boil, stirring constantly, for 10 to 12 minutes or until candy thermometer reaches 234° to 240º F (soft-ball stage).
Quickly stir in white chocolate chips, marshmallow crème, 3/4 cup walnuts and vanilla extract. Stir vigorously for 1 minute or until morsels are melted. Immediately pour into prepared pan and top with remaining 1/4 cup walnuts. Let stand on wire rack for 2 hours or until completely cooled. Refrigerate tightly covered. To cut, lift from pan; remove foil. Cut into 1-inch pieces.
Source: adapted from Very Best Baking