I believe that I have read something along this before but I didn't understand completely. I have read that someone added a box of pudding and an egg to make more batter to a box cake. The pudding is it instant or the cooked kind? And the size of the box small or large. Thanks for your help.

It is a small box of instant pudding and an extra egg. You can add the flavor of pudding that is closet to your cake flavor (vanilla for white or yellow cake) or you can mix it up a bit. I love adding white chocolate or cheesecake pudding to my vanilla cake. It gives just a hint of a different flavor from a plain box mix.
I'm not sure how much extra batter it makes though.

The recipe that is called"durable cake for 3d and wedding cakes" is in most saved recipes.
I use it all the time,and it is so good.It uses sour cream along with a small(3.5oz)box of instant pudding and the box cake mix.