Prepare a 9X13 baking pan by lining it with parchment paper.
Preheat the oven to the temperature recommended on the box mix.
Prepare the brownie mix according to the directions on the package and bake for the recommended time and allow them to cool.
While the brownies are cooling, prepare the peanut butter layer and then the ganache layer.
With a hand mixer, beat until smooth the icing sugar, peanut butter, butter, vanilla and salt. This will end up as a thick, playdough consistency. Set this aside.
Next we will make the ganache. Measure the chocolate into a medium sized glass bowl (you will need a lid or plate that will cover this) and set this aside.
Melt the butter over medium heat in a small saucepan. When the butter is melted, stir in the cream.
Whisk this together constantly while increasing the heat to medium high. Cook this until it just starts forming bubbles.
Immediately, pour the cream mixture over the bowl of chocolate and cover it with the lid. Let this sit for 5 minutes.
Then stir to combine the chocolate and cream mixture. It may take a minute or two of stirring, but you should create a smooth ganache.
As the ganache cools, it will thicken slightly. That is fine. Just stir it up again when you are ready to spread it.
Once the brownies have cooled a bit, spread on the peanut butter mixture by scooping out spoonfuls of the mixture onto the brownie layer, then using a spatula to smooth it out and cover the brownie layer completely.
Pour the ganache on top and smooth out.
Place the buckeye brownies into the fridge to allow them to cool and set for easier cutting. They will need at least ½ an hour.