Combine brownie mix, eggs, water and oil in a large bowl, beat with an electric mixture until combined
Remove half the brownie mix and set aside
Spread remaining brownie mix evenly into prepared pan
Whisk together sweetened condensed milk and peanut butter until smooth
Spread evenly over brownie mixture in pan
Separate the remaining brownie mixture into pieces, flatten them with your finger or a spoon and place them on top of brownie mixture in the pan, spread them out so they are randomly covering the peanut butter.
Bake for 25-30 minutes or until top is set and edges are slightly brown