Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with butter or non-stick spray. In a large mixing bowl, combine the cake mix, water, vegetable oil, and eggs. Beat everything together with a hand or stand mixer until smooth and fully combined. Pour the batter into the prepared baking dish and spread it out evenly.

Place the baking dish in the preheated oven and bake for 25 to 30 minutes, or until a toothpick inserted into the center of the cake comes out clean. Once baked, remove the cake from the oven and allow it to cool in the dish for about 10-15 minutes.

While your cake is cooling, prepare the peanut butter topping. In a mixing bowl, combine the peanut butter, powdered sugar, vanilla extract, milk, and flour. Use an electric mixer to beat the mixture until smooth and creamy.

Once the cake has cooled slightly, spread the peanut butter mixture over the top of the cake. Make sure it is evenly distributed across the surface.

In a saucepan over low-medium heat, melt the chocolate chips with 1 tablespoon of vanilla extract. Stir the chocolate occasionally until it is completely smooth and melted. Be sure not to overheat the chocolate.

Once the chocolate is melted, pour it over the peanut butter topping. Use a spatula to spread the chocolate glaze evenly across the entire cake.

Let the cake cool for 10 minutes at room temperature before slicing. You can refrigerate the cake for about 30 minutes to allow the layers to set, or you can serve it immediately. Slice into squares and enjoy!