How should I make this cake?

My friend LOVES pistachio pudding and wants a cake with pistachio pudding in it for her birthday. I was thinking either taking a white cake mix and adding a packet of instant pistachio pudding to it, or I was also thinking just make a layer white cake and put pistachio pudding in between the layers. Which would be better? Also, what kind of frosting would be good on this type of cake?