Preheat the oven to gas 6, 200°C, fan 180°C. Peel and finely chop the onions, peel and finely slice the garlic, and place it all in a large nonstick pan on a low heat with 1 tbsp oil. Strip in most of the thyme leaves and cook for 15 mins, or until softened, stirring regularly.

Meanwhile, peel the mushrooms and remove the stalks, finely chopping the stalks and peeling and adding to the veg pan as you go. Brush the mushrooms with 1 tsp oil, then arrange cup-side up on a large baking tray. Sprinkle with a pinch of black pepper and pop in the oven for 15 mins.

Strip the remaining thyme into a food processor with the hazelnuts, tear in the bread, add 2 tsp oil and blitz into rough crumbs.

Add 1 tbsp vinegar to the veg pan and stir in the spinach (in batches, if needed) with a good grating of nutmeg. Cook for 10 mins, or until any liquid has evaporated. Remove the mushroom tray from the oven and spoon the mushroomy juices into the spinach, then divide the spinach mixture between the mushrooms. Sprinkle over the nutty crumbs, grate over the cheese (if using) and baking for another 20 mins, or until golden.