In a small bowl, combine the yogurt, cheese, parsley, sour cream, and pepper; cover and refrigerate.
In a large kettle, cook the fusilli according to package directions, omitting the salt.
Meanwhile, heat the olive oil in a heavy 7 inch skillet over moderately high heat for 1 minute.
Add the mushrooms, onion, and garlic and cook, stirring occasionally, for 5 to 7 minutes or until the onion is soft.
Add the wine to the mushroom mixture and cook for 1 to 2 minutes or until most of the liquid is absorbed.
Add the yogurt cheese mixture and heat through; do not boil or the sauce will curdle.
Drain the fusilli and return it to the kettle.
Add the mushroom mixture and toss well with two forks to mix.
Transfer the fusilli to a heated platter and garnish with parsley sprigs, if desired.