Grease a 13×9 casserole dish and preheat oven to 350 degrees.
In a small bowl, combine flour, baking powder, baking soda and salt. Whisk together and set aside. In a second small bowl, combine 1/2 c. sugar with 2 t. cinnamon and set aside.
In a mixing bowl, beat together 1 c. granulated sugar, brown sugar and butter until creamy. Stir in eggs, sour cream and vanilla until fluffy. Slowly add flour mixture to mixing bowl and combine.
Spread half of the batter into prepared casserole dish. Sprinkle with half of the cinnamon-sugar mixture. Top with 3/4 c. chocolate chips. Carefully spread remaining batter on top of chocolate chips and repeat topping, using the rest of the cinnamon-sugar and 3/4 c. chocolate chips.
Bake at 350 degrees for 30-35 minutes, until golden and a toothpick inserted in the center comes out clean.
If desired, melt the remaining 1/4 c. chocolate chips in a small bowl in the microwave and drizzle over cooled coffee cake.
