Pour boiling water over the dried porcini mushrooms in a bowl and let them steep for 30 minutes. Then drain, wash briefly and chop.
Pour light vegetable stock - which shouldn't be too salty - into a saucepan and keep warm.
Heat the olive oil in a large saucepan and fry the spring onions and garlic in it. Add the rice and cook until translucent. Deglaze with white wine. Add the vegetable broth, ladle at a time, and let the rice absorb it while stirring. The rice should be firm to the bite after about 20 minutes. The consistency of the risotto should be creamy. If it is too dry, add more stock.
In the meantime, heat the rest of the olive oil in a pan and fry the mushrooms over a high heat for about 4 minutes until they are lightly browned. Add soy sauce and stir-fry for 2 more minutes. Take it off the stove.
Put stir fried mushrooms, grated lemon zest, parsley and butter (or olive oil) into the risotto. Season with salt and freshly ground black pepper. Optionally serve with parmesan.