Beat the cream cheese and peanut butter together until smooth. Mix in the powdered sugar and then mix in the cool whip, scraping the sides of the bowl as needed.
Spread a couple tablespoons of the mixture on the bottom of a 9x9 inch cake pan. Arrange graham crackers in the bottom of the pan, cutting them as needed to fit. Spread a third of the filling on the graham crackers and then layer two more times with crackers and filling. Cover with plastic wrap and refrigerate for at least 3 hours.
For the Ganache:
Place chocolate chips and peanut butter in a bowl. Heat the whipping cream and pour over the chocolate, cover for 2 minutes and then mix until smooth. Place in a baggie cut the tip and drizzle over the top of the cake. Sprinkles with chopped Reese's