Just get yourself a small chocolate Orpington bantam or LF. Chocolate is sex linked so a : chocolate orpington cock over a black ameraucana hen will give you = chocolate pullets and black cockerels split chocolate. OR black cock ameraucana over a chocolate orpington hen will give you only black cockerels split chocolate and pullets that are worthless for the project since they will only be pure blacks and will not produce any chocolate offsprings. This is a very simple project for producing chocolate color but you will have to correct leg color, combs, and the production of muffs and beards plus the feathers will be loose from the Orp and need to tighten them up, not to forget egg color as well.
I have been trying to understand what "split" chocolate or "split" black means and haven't been able to figure what it means so I'll ask straight out -- if someone could explain it in not-too-technical terms?
Also, with using a Chocolate Orp for breeding I would think the Chocolate Ameraucana ultimately will have more greenish eggs rather than bluish eggs -- sort of the way Lavender Amers seem to be laying more greenish also. Not that there's anything wrong with greenish shells but we really enjoyed seeing the blue shells from our Blue Wheaten.