Put the dried mushrooms in a bowl and pour over 100ml hot water. Leave to soak for 30 minutes. Drain, reserving the liquid, and chop.
Cook the onion in 1 tbsp oil and half the butter, until soft. Add the garlic and cook for another minute, then add the soaked mushrooms and cook for 2 minutes, stirring.
Add the rice and stir over a low heat for 1 minute, then add the white wine, if using, and simmer until it has almost evaporated.
Add the reserved mushroom liquid and the hot stock, a ladleful at a time and stir. Make sure the hot stock has been almost absorbed before you add the next ladleful. Stir frequently and continue cooking for 12 minutes.
While the risotto is cooking, heat the rest of the oil and butter in a frying pan and cook the sliced fresh mushrooms until they shrink. Add to the risotto with the pan juices and the peas and continue cooking, adding the stock, a ladleful at a time, until the rice is tender and creamy.
Stir in half the chopped parsley. Serve the rest sprinkled on top.