Make the strawberry cake according to package directions. In the meantime, make some strawberry creme pudding, only don't use as much milk. If the directions call for 2 cups cold milk, use just 1.5 cups. (Or, if you really want something rich, use whipping cream instead of milk).
Once the cake is cooled, you can either use the pudding as frosting, or just glop it on top of your piece of strawberry cake. It's a really nice and creamy dessert. I'm not a big fan of traditional frosting, so I prefer my "frosting" in a modified form of pudding.
Please note my future recipe posts will now be over at ScreamingSardine because blogger screwed up one too many times.