You can do anything with them that you do with cabbage, really. I'll eat them raw and shaved as a salad, or flash fried, but the way I actually like them requires a high wire cooking act.
Toss in oil and salt in a bowl, then roast them, hard. Like 425/220 for temp and I use convection, maybe 30-40 minutes depending on size. They eventually turn mahogany brown, and the insides are creamy ans sweet. Brown, not black! Toss them in the oil bowl half way through for better browning.
The problem is that just a few minutes under and they don't have the crisp, a few minutes over and they dry out and become just crispy shells. Which are good, unless they turn to carbon. So there's a 5 minute window where you really have to pay attention, as they go from not quite done to carbonized. Taste test helps at this stage. They are 100% different at this point from any other form of preparation. And it's too finicky for restaurants to do this, which is why you usually see flash fried,
A bit of bacon, a bit of parm, either or both is a good finish. Just recently I used some maple syrup/soy/white balsamic to dress them on the plate, and that was a good change. I'm going to see what I can do with that maple mix in terms of glazing for fish or other veg too.