Cook orzo according to the package instructions, drain and place in a large mixing bowl. Immediately grate Parmesan cheese into the bowl with pasta before pasta cools. Mix well until cheese is melted and pasta is all coated.
While pasta is cooking, prepare mushrooms and shallots. Peel and thinly slice shallots. Wash and thinly slice mushrooms. Preheat a large cooking pan over medium heat and add truffle oil. Add onions and sauté until translucent. Add mushrooms, season with some salt and cook until mushrooms are done.
Add cooked mushrooms and shallots to the bowl with Parmesan orzo. Mix well. Taste to adjust for more salt.