Instructions for Batter:

1. Preheat oven to 350°F.
2. Combine butter, brown sugar, and granulated sugar well.
3. Add 1 egg and mix until incorporated.
4. Sift the flour, baking powder, baking soda, and salt together. Add half into the batter mix and beat until well mixed.
5. Add the sour cream and vanilla. Mix well.
6. Add the remaining flour and mix until well combined.
7. Add the second egg and beat well.
8. Grease an 8 x 8 pan and pour ¾ of the batter in.

Instructions for filling and assembly:

1. Combine the brown sugar, cinnamon and chocolate chips and sprinkle ¾ over top of the batter.

1. Dot the remaining batter on top and with a knife or spatula, swirl it in.
2. Top with the remaining filling mix.
3. Bake on middle rack for 30 minutes or toothpick comes clean from the middle and the sides have started to pull away from the pan. Turn oven off and leave in the oven for 10 minutes.
4. Remove and let cool. Cut into 9 pieces.