Thanks, Those are my d'anvers. Was just about to bring them up when I saw this thread. Im not a orp guy, but can tell you how to easily make them.
barred or cuckoo male to lavender females
You MUST use the barred/cuckoo male
by doing this , all offspring will be barred , they will be single fatcored offspring meaning they have 1 copy of the barring gene in them and thus will have a few un barred feathers, and lavender is recessive so they will all be black barred birds the first time, but will be split for lavender.
So now, take the barred males from this breeding and cross them to the lavenders 1 more time and you will have them, still single factored at this point. But now that you have both male a female lavender barred birds, when you cross them back to each other they will get 2 copies of the barring gene and all feathers will be barred.
or you can also cross the males back to their sisters from the first breeding and get some that way too ( these would be double factored as both parents were barred and all feathering will be barred).