What do I do with leftover egg yolks?
I'm making a cake that only requires the whites.
You should consider making a vanilla pudding with leftover egg yolks. It is a nice recipe to make, where yolks add lot of richness to the pudding, which gives it a silky texture. You can also make classic creme brulee. Visit http://bakingbites.com/2012/05/5-recipes-that-use-up-leftover-egg-yolks/ for more details.
Throw them out..
Make an omlet in the mourning1 :)
Cook them up and feed to the dog, her coat will be very shiny,but only if u have a dog u love!