Preheat the oven to 375°F (190°C).
In a mixing bowl, combine the crushed graham crackers and sugar. Stir in the melted butter until well mixed. Press this mixture firmly against the sides and bottom of a pie plate.
Bake the crust for 8 minutes, then let it cool completely.
Spoon the hot fudge sauce into the bottom of the cooled crust, spreading it into an even layer. Freeze the crust for 10 minutes to set the fudge.
In a large bowl, beat the peanut butter and milk until well blended.
Add the instant pudding mixes and beat for about 2 minutes until the mixture thickens.
Gently fold in the Cool Whip and chopped peanut butter cups.
Spoon the peanut butter filling over the chilled chocolate layer and refrigerate it to set.
Using an electric stand mixer with the whisk attachment, beat the heavy cream until soft peaks form.
Add the powdered sugar and vanilla, then continue whisking until stiff peaks form.
Spread the whipped cream over the set peanut butter layer.
Garnish the pie with additional mini Reese’s peanut butter cups.
Chill the pie in the fridge for at least 3 hours before serving.