Prepare a 9x13-inch baking pan by spraying it with non-stick cooking spray and lining it with parchment paper, set aside.
Preheat the oven to the temperature recommended on the box mix.
Prepare the brownie mix according to the directions on the package.
Bake the brownies for the recommended time on package, remove from the oven and allow them to cool.
While the brownies are cooling, prepare your peanut butter layer. In a medium sized bowl add the butter, powdered sugar, peanut butter, vanilla extract and salt.
With a hand mixer, beat this together until smooth. This will be on the thicker side, set aside.
To make the ganache. Add chocolate into a medium sized glass bowl (you will need a lid or plate that will cover this) and set this aside.
In a small saucepan, melt the butter over medium heat, once melted stir in the heavy cream. Whisk this mixture constantly while increasing the heat to medium high. Heat until it just starts forming bubbles.
Immediately, pour the butter and heavy cream mixture over the bowl of chocolate and cover it with the lid. Let sit for 5 minutes.
After 5 minutes, remove the cover and stir combing the chocolate and cream together until you get a smooth melted consistency.
As the ganache cools, it will thicken slightly which is fine, just stir ganache when you are ready to spread it.
Once the brownies have cooled, with a spoon dollop of the peanut butter mixture over the brownies.
Using an offset spatula, smooth the mixture out to cover the brownie layer completely.
Pour the ganache on top and again with an offset spatula smooth out covering the peanut butter layer.
Place the brownies into the refrigerator and allow them to cool and set for at least 30 minutes for easier cutting.