Make fusilli and set aside

In a small bowl, combine the yogurt, cheese, parsley, sour cream, and pepper; cover and refrigerate

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

Cook fusilli al dente, drain well and return to the cooking pot

Add the mushroom mixture to the pot and toss well with two forks to mix

Transfer the pasta to a heated platter and garnish with parsley sprigs, if desired.