Preheat the oven to 350 degrees. Lightly grease a 9-inch pie plate with cooking spray or butter. Set aside.
In a medium bowl, pour the sugar, cocoa powder, flour, and salt. Stir together until well combined. Next, add the melted butter. Mix until a chocolate dough forms.
Transfer the chocolate dough to the prepared pie dish. Using your hands and fingers, push the dough firmly into the corners and sides of the pie plate. The crust should be of even thickness all over.
Pierce the bottom and sides of the pie crust with a fork to prevent air pockets in the pie crust from forming while the pie bakes.
Bake the pie crust for about 10-12 minutes. Remove from the oven, and set on the countertop to cool completely.
In a stand mixer, fitted with a whisk attachment, whip a 1/2 cup of the heavy cream on medium speed, about 2 minutes. Next, adjust the speed to medium-high until you reach soft peaks. Spoon out the whipped cream into a small bowl. Set the bowl of whipped cream aside to chill in the refrigerator.
In a stand mixer, fitted with a whisk attachment, beat the cream cheese, powdered sugar, and salt until smooth and creamy. Next, add the peanut butter. Mix until well combined. The filling will not appear as smooth with the peanut butter, but don't worry!
Remove the bowl of chilled whipped cream from the refrigerator. Using a silicone spatula, gently fold the whipped cream into the peanut butter mixture. The mixture will become extremely smooth. Next, carefully fold in the mini chocolate chips. Set the peanut butter mixture aside on the counter while you prepare the chocolate ganache.
In a small saucepan, over medium heat, pour 1/4 cup of heavy cream and heat to a simmer. Meanwhile, break up the baking bar chocolate and add to a medium bowl.
Once the cream begins to simmer, pour over the chocolate. Do not stir. Cover with plastic wrap and set aside for 5 minutes. After 5 minutes, whisk until smooth.
Pour about 3/4 cup of the chocolate ganache into the cooled chocolate pie crust. Using the back of a spoon, spread an even layer of the ganache in the bottom of the crust. Refrigerate until the chocolate ganache layer firms slightly.
Once the chocolate ganache feels tacky to the touch, spoon the peanut butter filling on top of the chocolate ganache layer. Using the back of a spoon, smooth the top of the pie. Using a whisk, drizzle the remaining melted chocolate ganache on top of the peanut butter pie. If the ganache has hardened, heat it up in the microwave in 10-second intervals. Chill in the refrigerator for 3-4 hours before serving. Enjoy!
If ganache seems too thin, feel free to add a handful of chocolate chips to thicken the ganache. If the ganache appears too thick, add more heavy cream. Microwave in 10-second intervals and whisk in-between until you achieve your desired consistency.