Pour brownie batter in a 9x9 square baking pan. You may want to reserve about 1/2 of the batter to prevent the brownies from being too thick and baking uneven (the box mix is made for 9x13). Bake the brownies following the instructions on the box. Set aside to cool for 30 minutes. Chop the chocolate chips for the ganache and add it to a large heatproof bowl. Set aside.

Pour the heavy whipping cream into a microwave safe bowl (I like to use a glass measuring cup) and heat in the microwave for about 45 seconds-1 minute. Make sure to keep an eye on it so it doesn't bubble over in the microwave. Pour the warm heavy whipping cream over the chocolate, cover with saran wrap and let it sit for 2-3 minutes.

Start whisking slowly and gently in the middle of the bowl, and continue whisking in one direction until the mixture is smooth and well combined. Whisking abruptly will cause air bubbles. Allow to cool for about 10-15 minutes. Using an offset spatula, spread ganache evenly over the brownies. Cover pan and set aside in the freezer while preparing the peanut butter layer.

Mix together the saltines, graham crackers, melted butter and powdered sugar together in a medium bowl. Stir in 1 cup of peanut butter and vanilla extract and combine. Carefully press the peanut butter mixture evenly over the ganache layer. I use gloves for this step.

Melt remaining 2 Tablespoons of peanut butter with 1 cup chocolate chips in the microwave for 30 second increments until 70% melted.  Stir until smooth and spread over peanut butter layer evenly. Top with peanuts (optional)

Chill in the refrigerator until completely firm, at least 2 hours. Allow to sit at room temperature for 10 minutes before cutting. Serve chilled to ensure the bars are firm. Setting them out for a few hours at room temperature for serving is OK. Cover leftover bars tightly and refrigerate for up to 1 week.