Experimenting with extract brewing and black walnuts

I am still new to homebrewing. I've done six brews so far. All extract and two of them are gluten free done with sorghum. (My girlfriend is Celiac.) A buddy of mine has a black walnut tree and suggested I try to use some in a homebrew. Every thread I have been able to find using black walnuts (or any nuts) has been all-grain. I'm not comfortable with doing all-grain yet so I am wondering if anyone has any suggestions on how to use extract and still make a black walnut beer.