I've never seen any chocolate cochins, and for htat matter, haven't heard of anyone breeding them, either with dun or choc. On the other hand, I've been working on chocolate silkies for years.
My bad! I confused the fluffy butt Chocolate Orps for Cochins! Cochins come in so many variations I made too hasty a remembrance.
Fantastic that you are working on Chocolate Silkies - could Choc Orps be used in the cross-breeding or is that too large a breed to work with Silkies? I'm not knowledgeable about genetics but sometimes it amazes me what cross-breeds are used to get certain colors. Example: My Buff Leghorns had Buff Orp, Buff Minorca, Buff Rock, and even Phoenix in her history. Some of these mixes were evident in one bird's body type yet her sister looks very Leghorn sleek in comparison. Never know what comes out in a mix when you go for certain colors or body types. Rather than culling I asked the breeder for pet quality and got 2 Buff Legs of which one happened to turn out as a good type and would be good for breeding.