Preheat oven to 350°.
Line a loaf pan with tin foil, and spray with non stick cooking spray. Set aside.
In a medium sauce pan, melt chocolate chips and butter over low heat. Stir around occasionally until everything is melted down and smooth.
Remove from heat and add in brown sugar and egg. Mix until well combined.
Add in flour, and mix until well combined.
Pour brownie batter in lined loaf pan.
In bowl of a stand mixer, or handheld mixer, cream together butter and sugar for the butter cake layer.
Add in eggs and milk. Mix until smooth and well combined.
Add in flour and baking powder. Mix until you have a nice smooth batter.
Pour butter cake batter over brownie batter. Using a spatula, carefully spread butter cake batter all over brownie batter.
Bake in preheated oven for 45-50 minutes, or until center isn't jiggly, and toothpick comes out clean from center.
Enjoy!