Soak mushrooms: According to the packet's instructions, rinse the porcini mushrooms and soak them in cold water for 20-30 minutes, according to the packet's instructions. Strain but keep the soaking water.
Heat the stock in a small pot and keep it simmering on very low heat while cooking the risotto.
Saute vegetables: In the meantime, finely chop the onion and the carrot. Heat the oil in a non-stick pan and cook the onion and the carrot until the onions are translucent.
Add the risotto rice and stir for about 1 minute until the rice starts to get translucent.
Add the white wine and keep stirring until the wine has cooked into the rice. Add a pinch of salt and stir.
Start adding the vegetable stock and 1 cup of the soaking water one ladleful at a time while stirring very often. Only add the next ladleful of liquid when the rice has absorbed the previous one.
Cook the rice for about 20 minutes or according to the packet's instructions. Keep tasting it towards the end of the cooking time; it should be cooked but still have a slight bite. If the rice is not entirely done yet, but you are out of stock, add some more of the porcini soaking water.
Take off the heat and stir in the butter and the freshly grated hard cheese or Parmesan. Adjust the taste with salt and pepper.