Preheat oven to 350 degrees F. Spray a 9x9 baking pan with non-stick spray; set aside.
In a large bowl, combine brownie mix, eggs, and oil and use electric mixer on medium speed until combined.
Set aside half of the brownie mixture and spread the remaining brownie mixture evenly into baking pan.
In a medium bowl, whisk together sweetened condensed milk and peanut butter until smooth. Pour and spread on top of brownie mixture in pan evenly.
Using a teaspoon, scoop small bits of the remaining brownie mixture and place randomly on top of the peanut butter mixture and press them down lightly using the bottom of the spoon into the peanut butter mixture.
Bake in the preheated oven for 25 to 30 minutes or until top is set and edges are lightly browned.
Place brownies on baking rack.
About 5 - 10 minutes after taking brownies out of oven, sprinkle ¾ cup of the Reese's Peanut Chips and ¾ cup of the Milk Chocolate Chips on top of the buckeye brownies while they are still hot and let them sit. In a few minutes, go back and spread the melted chips evenly.
In another 20 minutes, sprinkle the rest of the chips and salted peanuts on top of the melted chocolate and cool completely. Cut into bars. Makes 20 - 25 bars.
Don't overbake, you want these to be gooey...but we don't want raw.