Heat 2 2/3 cups of the milk in a large saucepan over medium heat until hot but not boiling. Whisk the granulated sugar, cornstarch and salt in a large bowl. Whisk in the egg yolks and the remaining 1/3 cup milk. Whisk half of the hot milk into the egg mixture until smooth, and then gradually whisk the egg mixture into the pan with the remaining milk. Cook over medium heat, whisking constantly, until the mixture boils and thickens, 6 to 8 minutes. Remove from the heat and whisk in the peanut butter until melted. Transfer to a bowl and cool slightly, stirring a few times to prevent a skin from forming. Pour the filling into the crust, smoothing it out so that it reaches the edges of the pie crust. Press plastic wrap directly onto the surface and chill until set, at least 4 hours.
When ready to serve, whip the heavy cream and confectioners' sugar in a large mixing bowl with a hand mixer until medium/stiff peaks form.
To assemble, top the pie with the whipped cream and garnish with peanuts and chocolate chips.