Melt 1/2 the butter in a frypan over medium heat. Stir in the onions and cook until golden brown. Mix in risoni, mushrooms and remaining butter. Cook and stir 5 minutes until butter is melted and mushrooms are tender.
Pour water and wine into the frypan and bring to a boil. Reduce heat to low. Season with garlic powder, salt and pepper. Cook 7 to 10 minutes until risoni is al dente. Stir in the Parmesan cheese and parsley to serve.