I just make it the same as the top part. I like my vegetables only just softened (pretty much just warmed through) so sometimes I have to put the stem in a little earlier than the rest unless I cut it up a little finer.
I will have it steamed, lightly fried, chop it finely and add it to peas and corn, soups, stir fry, omelette/quiche type stuff, through salads. We even chop it finely and fry it with chopped bacon then mix it with Mac cheese...yum. I think you can use it with anything that you enjoy to eat with it any other time. I think the only thing I haven’t done with the stem is roast it, but... I might give that a go soon with some bacon cheese and garlic, I reckon it would be nice.