Stuffed Red Onions with Barley, Mushrooms and Thyme

An Onion with Room for More

Red onion does more here than add flavor: the hollowed-out onions become soft, edible little bowls. Roasting them first makes the layers tender and milder in flavor, while the outside stays sturdy enough to hold the filling. Use large, firm onions and hollow them out carefully with a teaspoon. Leave a few layers around the outside and save the scooped-out flesh; finely chop it and add it to the mushrooms later. Set the onions upright in a baking dish so they don’t tip over.

Pearl barley gives the filling a pleasant bite and makes the dish hearty enough to serve as a main. Cook the barley in plenty of water until tender, tasting it toward the end: the grains should be soft but not falling apart. Cooking times vary by brand, so follow the package directions too. Drain the barley well before adding it to the mushrooms. Don’t have pearl barley? Use spelt berries and adjust the cooking time according to the package directions. They usually have a slightly firmer bite; rice is less suitable as a direct substitute because its texture and absorption are different.

Cook the mushrooms in a large, hot frying pan, giving them time to brown first. If the pan is too crowded, they’ll release moisture and steam rather than fry. Cook them in two batches if needed. Button mushrooms are convenient, but chestnut mushrooms, oyster mushrooms or a mixed mushroom medley work too. Add the finely chopped onion center once the mushrooms start to brown. Thyme complements their earthy flavor; a splash of vegetable stock keeps the mixture juicy without making the filling wet.

The filling can look a little firmer in the pan than you want it to be when served: the barley will absorb a little more liquid in the oven. A little lemon juice at the end cuts through the sweetness of the roasted onion and the mushrooms’ rich, savory flavor. So taste the filling after adding the barley, then season with salt and pepper. Fresh thyme leaves add a distinct herbal note; if using dried thyme, use a little less, as its flavor is more concentrated.

Serve the onions straight from the baking dish, scattering the roughly chopped hazelnuts over them just before eating so they stay crunchy. A simple green salad with a tart vinaigrette goes well alongside and makes the meal feel lighter. Once cooled, leftovers can be covered and stored in the refrigerator for up to three days. Reheat them in a baking dish covered with foil until piping hot; add a small splash of water or stock if needed to keep the filling juicy.