Preheat oven to 350 degrees. Grease a 13x9 inch baking pan with shortening.
In the bowl of an electric stand mixer combine the flour, 1 1/2 cups sugar, baking powder, baking soda, salt, sour cream, butter, vanilla and eggs. Beat on low speed for 3 minutes or just until ingredients are well incorporated.
Pour half of the batter into the prepared baking pan. Combine the 1/2 cup of sugar and cinnamon, stir to combine. Sprinkle half the cinnamon sugar over the batter evenly. Sprinkle 1/2 the milk chocolate chips over the cinnamon sugar. Using a large spoon, drop the remaining batter in dollops over top. Gently spread the batter over all to cover the cake. Sprinkle the remaining cinnamon sugar and chocolate chips over the top of the batter. Bake at 350 degrees for 35 - 40 minutes. Testing with a tooth pick for doneness. Remove from oven, cool on wire rack.