I do this almost every time I prepare endive (which to be fair, is about three times per year). But I half it and pop it in a bag with some oil and salt at 85C and let it go for like 40-45 minutes. Then unbag while hot and let the surface moisture flash off. Then sear the cut half in copious butter and olive oil and garnish with flakey salt and chives.
Endive is relatively tender compared to cabbage, at least in my experience, so you don't need extended cook times to soften it. You can if you really want it to go all sogged-out braisey, but then you're making a different dish than I'm making. If you're not keen on bitterness, you can blend in some sugar with the salt when you season pre-bagging. A splash of vinegar can be nice too.
