Heat 2 tbsp of olive oil in a large pan over low-medium heat. Add the thinly sliced onions and a good pinch of salt and cook for 15-20 minutes, stirring occasionally. Add a splash of water if they start to stick. Don’t be tempted to turn the heat up, or you’ll risk burning the onions.
While the onions cook, remove the stems from the mushrooms and finely chop them. When the onions are softened and start to turn golden, add the sugar, balsamic vinegar and chopped mushroom stems. Cook for a further 5-10 minutes, until sticky and caramelised.
In the meantime, preheat the oven to 200°C (conventional). Place the mushroom caps on a lined baking sheet, lightly drizzle with olive oil and sprinkle with salt. Roast for 10 minutes.
Once the onions have caramelised, add the rosemary, walnuts and 3/4 tbsp of the Australian Bush Pepper blend and cook for a further minute. Set aside.
Take the mushrooms out of the oven and drain the water they have released. Place 2-3 tablespoons of the onion filling onto each mushroom and top it up with grated cheese. Put them back in the oven and roast for a further 10 minutes.
While the mushrooms are in the oven, add the breadcrumbs, 1 tbsp of tablespoon of olive oil, a pinch of salt and the remaining Bush Pepper blend to a pan and toast on a low-medium heat for a few minutes or until the breadcrumbs turn golden.
Take the mushrooms out of the oven, sprinkle the breadcrumb mix over the top and serve immediately.
