Preheat oven to 200˚C.
Using a very large sauté pan, (the veg will cook down) heat a drizzle of olive oil. Add the onion with a pinch of salt and cook until soft. Add the garlic and cook until fragrant. Add the cabbage and sauté until it begins to soften then add the kale. Pour in the chicken stock and simmer gently to braise the veg until very tender and juicy. Season to taste.
Mix miso paste and hot water together in a medium sized bowl until smooth. Add the sesame oil, soy sauce, garlic and chilli flakes. Mix well. Using a pastry brush, brush the mixture all over the portabellinis. Place on a baking tray and bake for about 7 minutes until tender, depending on their size.
When the kale and cabbage is beautifully soft and the stock has reduced, plate onto a serving platter. Top with the sticky roasted miso mushrooms.
Serve as a fabulous side dish or a vegetarian main along with some whole grains or legumes.