Heat a large skillet over medium heat. Sauté thinly sliced leek and shiitake mushrooms for 5-7 minutes. Add cream and sauté for another 5 minutes. Season with salt and pepper. Set aside.
In a different skillet sauté diced onion for 5-7 minutes, or until softened.
Add rice and stir for a minute.
Add wine and stir for another minute, until almost all liquid is absorbed.
Add 1 cup hot broth. Simmer until broth is almost absorbed, about 3-4 minutes.
Add more broth (1 cup at a time), allowing each additional cup to be absorbed before adding next.
Stir in leek and mushrooms mixture, then add parmesan cheese and truffle oil. Mix well.
Serve with chopped fresh parsley and black truffle.