½ loaf of bread, country bread, cut into 1.5 cm cubes, lightly toasted (about 300 g)
1 cup cashews, toasted and salted, coarsely chopped
¼ cup olive oil
1 cup vegetable stock
Cut off the top quarter of each onion with a knife and peel. Use a spoon to make a hole and remove most of interior, leaving about 2-3 outer layers and creating a shell.
Finely chop the parts of the onion that were removed (about 3 cups).
Add ¼ cup olive oil to a deep pan.
Add the chopped onions, celery, salt and pepper. Sauté over medium to high heat for about 5 minutes, stirring continuously until the vegetables soften.
Add the garlic and stir for 1 minute.
Add the spinach and sauté for 1 minute.
Transfer vegetable mixture to a large bowl. Add the bread cubes, cashews and ½ cup vegetable stock. Stir and set aside to cool.
Preheat oven to 220* C (428* F) Fan.
Place the onions in a 35×25 cm (5 cm deep) baking pan, cut side facing upwards. Add ½ cup of water to the pan and cover with aluminum foil. Place the baking pan in the oven on the middle rack. Bake the onions for about 25-30 minutes, until they soften but not to the point where they will fall apart.
Remove pan from oven and lower temperature to 180* C (350* F) Fan.
Transfer onion shells to a working surface and discard the water left in the pan. Fill the onion shells with the filling and return to pan.
If any filling is left over, put it in a shallow, greased baking pan. Add the remaining ½ cup of vegetable broth.
Bake the stuffed onions and the stuffing with the vegetable broth, uncovered, on the middle rack for 25-30 minutes.