FILLING:

5 tbsp flour
1 cup milk

 

Bake cake in 9x13" pan.  Bring filling to boil stirring until thick.  Cool (I like to put the pan in cold water to cool it faster, must be really cooled).  Beat remaining ingredients until fluffy.  Add filling mixture, beat until fluffy again.  Cut cake in 1/2 length-wise (using thread or dental floss makes it easy).  Put all of the filling on bottom 1/2 of cake and top with other 1/2. 

 

NOTE:  To make a Susie-Q cake using chocolate cake mix.