In a large frying or sauté pan, heat 2 big glugs of olive oil over medium heat.
Add the onions and garlic with a big pinch of salt and sweat until soft, 7 minutes or so.
Add the broccolini and hearty greens and toss to coat.
Add the beans and their pot liquor.
Increase the heat to high to bring to a boil, then lower to a low simmer and cook, uncovered, until the broccolini and greens are just about to fall apart, 15 to 20 minutes.
If it starts to get dry along the way, add a bit of water.
Add the vinegar if the dish needs a bit of pep.
Serve with bread to soak up the liquid and several gratings of any hard cheese, if you like.
