In a medium saucepan, bring the broth, water, and soy sauce to a gentle boil. Add the porcini mushrooms and allow them to simmer until tender, about 5–10 minutes. Lift them out, finely chop, and keep the broth at a soft, steady simmer.
In a large, heavy-based pot or Dutch oven, melt the butter with the olive oil over medium heat. Add the onions and cook slowly until softened and translucent, about 8 minutes, allowing their sweetness to develop without colour.
Stir in the cremini mushrooms, chopped porcini, and garlic. Sauté until tender and their moisture has fully evaporated, concentrating their flavour.
Add the Arborio rice, stirring to coat each grain in the buttered base, and toast gently for 2–3 minutes. Pour in the white wine and allow it to reduce until fully absorbed, leaving behind its delicate acidity.
Begin adding the hot broth, one ladle at a time, stirring with patience and intention. Allow each addition to be absorbed before introducing the next, gradually coaxing the rice to release its starch. Continue this slow process for around 30 minutes, until the grains are tender and the risotto achieves its signature, creamy consistency.
Finish by folding through the Parmesan and fresh parsley. Season carefully with salt and freshly ground black pepper, and serve immediately while warm and beautifully fluid.
