1. In a large bowl, combine the mashed potatoes, flour and salt. In another bowl, whisk the eggs, yolk and olive oil; add to potato mixture. Turn onto a heavily floured surface; knead for 3-5 minutes or until smooth. Divide into fourths. On a floured surface, roll each portion into a 3/4-in.-thick rope; cut into 1-in. pieces.
2. In a Dutch oven, bring water to a boil. Cook gnocchi in batches for 45-60 seconds or until they rise to the surface. Remove with a strainer. Serve spaghetti sauce over gnocchi; sprinkle with Parmesan cheese. Yield: 8 servings.