preheat the oven to 350°. butter an 8-inch square baking pan + set aside.
in a medium bowl, whisk together the flour, baking powder, baking soda, + salt. set aside.
using an electric mixer or a stand mixer, cream together the butter + 1 cup sugar until fluffy, about 5 minutes.
add in the eggs, one at a time, + beat until smooth.
beat in the sour cream + vanilla extract. mix until well combined.
slowly add in the dry flour mixture. mix until just combined.
in a separate small bowl, make the cinnamon-sugar topping/filling, by whisking together sugar, brown sugar, + cinnamon.
prepare the coffee cake: pour half the batter into the prepared cake pan, then sprinkle with half of the cinnamon-sugar mixture + half of the chocolate chips.
spread the remaining batter over the filling, spreading gently.
top with the remaining chocolate chips + cinnamon-sugar mixture.
bake until the top is golden + a toothpick inserted in the center comes out clean, about 40-50 minutes.
cool to room temperature + serve.
