milk (add more as necessary)
MIx cake mix, eggs, oil, and sour cream well.
Pour one-half of this mixture into a greased 9 x 13 pan.
In a separate bowl, mix brown sugar and cinnamon together and pour this mixture over the first half of the cake batter.
Add remaining cake batter over top of brown sugar mixture. Swirl top of batter with fork to incorporate the brown sugar throughtout the cake batter.
Bake 40 minutes at 325 degrees.
Remove from oven and cool completely. Mix ingredients for frosting and pour over cooled cake. (Can double the icing for more topping if desired).