Preheat your oven to 350°F (175°C). Line a 9×9 inch baking pan with parchment paper, leaving some overhang on the sides for easy removal. Set aside.
For the Brownie Layer:
In a mixing bowl, combine the melted unsalted butter and light brown sugar. Whisk until fully blended.
Add the eggs and vanilla extract, whisking again until the mixture is smooth and the eggs are fully incorporated.
Gradually add the all-purpose flour, baking powder, and salt to the wet ingredients. Stir until the batter is thick and smooth, switching to a rubber spatula if needed. Ensure the batter is evenly combined by scraping down the sides and bottom of the bowl.
Spread the brownie batter evenly into the prepared pan.
Bake the brownie layer for 25 minutes. Once baked, remove from the oven and allow it to cool while you prepare the banana pudding layer.
For the Banana Pudding Layer:
In a separate mixing bowl, use a handheld mixer on medium speed to beat the softened cream cheese until smooth and fluffy.
Add the instant banana cream pudding mix, large eggs, and whole milk to the cream cheese. Beat again for 30 seconds to 1 minute, or until the mixture is smooth and well combined.
Carefully dollop the banana pudding mixture over the cooled brownie layer, spreading it gently to the edges with a small offset spatula to create an even layer without disturbing the brownie layer.
To Garnish:
Arrange the vanilla wafer cookies in a grid on top of the banana pudding layer. Place the cookies in 4 evenly spaced rows, so they will sit in the center of each brownie square once sliced.
Bake the assembled banana pudding brownies for an additional 15-18 minutes, or until the pudding layer is lightly golden around the edges and set in the center. A toothpick inserted into the center should come out clean.
Remove the brownies from the oven and allow them to cool completely at room temperature before slicing and serving.