These onions are a bit of a revelation, and the very definition of low effort/high impact, where just a few ingredients come together to create something truly spectacular.
Still, the effort we save you on mise en place we take back by asking for a roasting pan that is just the right size. This is important. The pan should be just big enough to fit the halved onions in a single layer, without them overlapping. The onions will then shrink as they cook, creating the space the sauce needs to evaporate and thicken into a glorious gravy. If your pan isn’t big enough to fit the onions (that’s sixteen halves), then roast fewer, decreasing the rest of the ingredients proportionally (the cooking method and time stay the same).
The size of your onions is also important; they should be small, weighing about 5¼ oz/150g each. If you can’t get hold of small onions, use large shallots instead.
Last, saturate each onion (or shallot) half very well every time you baste, spooning the sauce over them several times so the cut sides remain moist. This is to ensure that the onions caramelize rather than burn.
These are best eaten straight out of the oven, but if you are making them ahead, warm the sauce up before serving, thinning it with a bit of water. Serve spooned over toast, rice, or mashed potatoes. Roasted chicken, predictably, is also a great match.
- Preheat the oven to 500°F/240°C fan.
- Halve the onions or shallots lengthwise, discarding the papery skin, as well as the layer beneath if it is tough or dry. Trim the tops and a little off the bottom (not too much—you want to ensure the onion halves stay held together at the base).
- In a medium bowl, whisk together the melted butter, miso, and warm water until fully combined.
- Place the onion halves, cut-side down and spaced apart, in a 9 x 13-inch/23 x 33cm high-sided baking dish or pan and pour in the miso water. Cover tightly with aluminum foil and bake for 35 minutes, then remove the foil and turn the onions over so they are cut-side up (take care to ensure they remain intact). Baste the onions very well, then return to the oven, uncovered, for another 45–50 minutes, basting every 10 minutes, until the onions are very soft, deeply browned on top, and the sauce has reduced to a gravy consistency.
- Carefully transfer the onions to a platter, pouring the sauce over and around them, and serve at once
Reprinted with permission from Ottolenghi Flavor by Yotam Ottolenghi and Ixta Belfrage copyright © 2020. Photographs copyright © 2020 by Jonathan Lovekin, except page 211 © Louise Hagger. Illustrations copyright © 2020 by Nishant Choksi. Published by Ten Speed Press, an imprint of Penguin Random House.