I bought a head of lettuce at the FM a couple of weeks ago. It was labeled, but I don't recall the name, and I can't find it in internet searches. The sign did say it was a relative of chicory.
It is the color of green cabbage, the shape of a napa cabbage (i.e., elongated rather than round like cabbage or flowery like fresh lettuce), with tightly bunched leaves the approximate texture of butter lettuce, but a bit thinner. Do you know what it might be?
The next question is how to cook it. It is bitter! And unlike other bitter greens than mellow a little with cooking, this one keeps its bitterness and moves it through the rest of the dish. I've tried it in a quick saute with garlic and cherry tomatoes, over pasta. Also sauteed and mixed into a quinoa pilaf with a few other ingredients aimed at providing a sweet counterpoint (sauteed shallots and zuchini). No luck. Just bitter bitter bitter.