Sounds like a good recipe! Just sampled my Bourbon Porter this weekend; I think Bourbon is a great flavor to go along with a robust porter. Not having a cask on hand, I added some toasted oak cubes along with 10 oz makers mark and 6oz Praline Pecan liqueur (pecan pie anyone?) to the secondary. It has a definite Bourbon/Pecan/Oak flavor but came out VERY smooth; mellow enough to drink a pint of, but it sure packs a punch! The flavor is great but not overwhelming. I would be interested in hearing how the vanilla goes for you; I have thought about using it, but have yet to try!

-Cameron