Cream butter; gradually add sugar, beating at medium speed of an electric mixer until light and fluffy.
Add eggs, one at a time, beating well after each addition.
Combine flour, baking powder, soda, and salt; add to creamed mixture alternately with sour cream, beginning and ending with flour mixture.
Spoon half of batter into a greased and floured 13- x 9- x 2-inch baking pan.
Combine chocolate morsels, brown sugar, and cinnamon; sprinkle 1 1/2 cups of chocolate morsel mixture over batter.
Top with remaining batter.
Sprinkle with remaining chocolate morsel mixture.
Bake at 350° for 35 to 40 minutes.