In a medium saucepan set over medium heat, combine 6 tablespoons of the sugar with the cornstarch. In a separate bowl, whisk together the milk and egg until fully blended. Gradually add the milk mixture to the saucepan, whisking constantly to prevent lumps. Bring the mixture to a gentle boil and cook for 1 minute, stirring continuously, until thickened. Remove from heat.

In a medium bowl, combine the pumpkin purée, vanilla extract, cinnamon, nutmeg, and salt, stirring until smooth. Slowly whisk the pumpkin mixture into the hot milk mixture until fully incorporated. Return the saucepan to low heat and cook for approximately 3 minutes, stirring constantly, until thoroughly heated. Do not allow the mixture to boil.

Divide the pudding evenly among four dessert bowls. Press plastic wrap directly onto the surface of each pudding to prevent a skin from forming. Refrigerate until chilled.

Line a baking sheet with aluminum foil and lightly coat with cooking spray. In a small nonstick skillet over medium-low heat, combine the remaining 2 tablespoons sugar, chopped walnuts, and a dash of salt. Cook, stirring frequently, until the sugar melts and coats the nuts evenly and turns golden in color. Transfer the walnuts to the prepared baking sheet and allow them to cool completely, then coarsely chop.

In a mixing bowl, beat the heavy cream at high speed until stiff peaks form. Top each serving of chilled pudding with approximately 2 tablespoons of whipped cream and sprinkle with the candied walnuts before serving.