Use cocoa powder rather than Bakers chocolate. The Bakers chocolate has an emulsifier that will cause the head to dissipate. I made an orange and chocolate porter using 8 ounces.
I simply split and scraped three vanilla beans into a jar with a lid and added enough light rum to cover the beans, I let it set for two weeks and strained it into my bottling bucket. It imparted a nice vanilla flavor to my 6.8 abv sweet potato porter.