Cook noodles until barely tender. Drain and pour into large serving bowl.
Meanwhile, cut meat across the grain into 1/8-inch-thick slices.
Pour 2 tablespoons olive oil into large pan or wok over medium-hight heat. Stir meat until browned on the edges but still pink in the center. Pour into another bowl.
Add remaining 2 tablespoons olive oil to pan. Add onion and garlic and stir until onion is limp. Add mushrooms and stir often until beginning to brown.
Add wine, cognac, and oyster sauce to mushrooom mixture. Bring to a boil, then simmer about 5 minutes.
Add cream and return to a simmer. In a small bowl. mix cornstarch with 2 tablespoons cold water until smooth. Add to mushroom mixture and stir until it boils and thickens.
Add sour cream and beef with any accumulated juices to pan and stir just until heated through, about 1 minute. Add salt and pepper to taste.
Pour beef Stroganoff over hot noodles. Sprinkle with parsley if desired. Serves 8.