I've had a thing about whole cooked onions ever since I was a child and we ate shepherd's pie for tea with a side order of boiled Spanish onions as the main vegetable. Boiling makes them very soft - if you can find the Spanish variety, which are pretty large, all you need to do is peel them, leaving the root intact, then bring to the boil on the hob and keep them on a medium simmer for about an hour.
However, baking them in their skins really concentrates the flavour and makes them very sweet.
What you need:
2-3 large whole onions
A little balsamic vinegar
What to do:
Make sure you choose onions with several layers of skin on - you don't want any that have just one thin layer peeling off and exposing the white flesh. Give them a wash under the cold tap if they have any mud on them and pat dry with kitchen paper.
Trim the roots very carefully with a small paring knife, just enough so they are flat enough to stand the onions upright. Put them in a roasting tin, sitting on the roots, and stick them in a very hot oven - 200-220C for a good hour.
When the onions are ready, you will find the skins quite blackened. Halve them across the root, sprinkle with a little balsamic vinegar and grated cheese, and season to taste. Then scoop the flesh out like you would a baked potato.
Because baking makes the onions very sweet, a salty cheese works best to accompany. Cheshire, Lancashire and Caerphilly are all good matches. You need a cheese that will melt a bit when it hits the hot onion, so despite its salty flavour feta is not such a good choice.
These make a meal on their own if you bake enough of them to sate your hunger. I roasted a couple of slices of belly pork, marinaded in chipotle sauce, for the plate above plus a side salad. Grilled bacon also works well, if you want meat, as do chops of some sort or even a steak.
Lovely as onions are, eating this sort of quantity does make you windy next day so be warned! But it also makes them ideal for lone diners...