It might be a species of Spigariello/Spigarello. Italian leaf broccoli. It's very good. The leaves are soft and the taste is not bitter like some cole type leaves. I got mine from Johnny's seeds. It does produce small heads but is mainly grown for the leaves.
Or it could be something else. Lots of the brassicas look alike. Do a google image search for Spigariello and see what you think.
Some are more frilly than others. This is what mine look like (though not quite as lush) (photo from the internet)