If they are already toasted then I would put them in a loose, large hops boil bag and suspend it by dental floss a little bit off the bottom of my serving keg. The nibs I bought were raw, so I spread them on a baking sheet and baked them at about 350° F. for maybe 15 minutes, turning, stirring, & mixing them at some time in the middle. I used 6 ounces for a strong but pleasant cocoa flavor in my pale ale. A porter could possibly handle more.