What do you do with the halved heads of garlic when they're cooked?

You eat them as part of the dish! They're fully cooked, and won't be like biting into sharp raw garlic, but if you don't like the idea of eating them as larger pieces, smash them to incorporate into the bean mixture (you can avoid the skins as you eat or pull out and discard them before serving if they bother you).

Squeeze them out of the garlic skin, serve with this dish or save in the fridge a few days to serve with salad or spread on baguette.