Soak 50g of dried porcini mushrooms in 1 liter of boiling water for 20 minutes. Lift out, squeeze and chop the mushrooms. Pour the liquid through a fine sieve, leaving the gritty sediment behind.
Dissolve 1 vegetable stock cube in the strained liquid and keep warm.
Heat 2 tablespoons of olive oil in a large pan over medium heat. Soften 1 finely chopped onion and 2 minced garlic cloves for 5 minutes. Add 250g of chopped cremini mushrooms and the porcini; cook for 8 minutes.
Stir in 300g of arborio rice for 1 minute. Add 175ml of white wine and simmer until absorbed.
Over medium heat, add the warm stock a ladleful at a time, stirring often and letting each addition absorb. Cook until the rice is tender and creamy, adding hot water if needed.
Remove from the heat. Stir in 25g of butter and half of 50g of grated Parmesan. Rest covered for 2 minutes. Season with salt and pepper; serve with the remaining cheese.
