Instructions: For the Fresh Tagliatelle: Mound flour in the center of a work surface, forming a well in the center. Crack the eggs into the well. Add oil and salt. Beat eggs with a fork until smooth. Gradually work flour into the eggs. Use a bench scraper to work in the rest of the flour, a bit at a time. Once all the flour has been incorporated, start working the dough with your hands to form a rounded mass for kneading. Be sure the work surface is clean of all loose bits of dough; lightly dust with flour. Knead the dough until smooth and elastic, about 10 minutes. Cover dough with an inverted bowl or plastic wrap; allow to rest 1 1/2 hours, or chill overnight.

Divide dough into large walnut-sized pieces. Quickly knead and flatten each portion of dough into a disc; very lightly dust with flour. Feed through a pasta machine set at the machines widest setting. (If pasta pulls or tears when passing through machine, simply sprinkle a little more flour over dough, just before its fed, to keep it from sticking. When finished, remove excess flour with a dry brush.) As the pasta sheet emerges, gently support it with your palm, and guide it onto work surface. Fold the sheet lengthwise into thirds. Repeat sequence twice on the same setting to smooth dough and increase its elasticity. Thin the dough by passing it through even finer settings, one pass on each setting from widest to narrowest (machine settings differ, some have as many as ten, others only six). Repeat with remaining dough. Pass each portion of dough through cutting blade for desired thickness. To cut by hand, lightly fold sheets one at a time into thirds. Cut with a sharp knife into desired thicknes

Bring a large pot of salted water to a boil. Remove stems from mushrooms and thinly slice to yield about 1 cup. In a small skillet, heat olive oil over medium heat. Add prosciutto, mushrooms, and parsley. Saute until light golden brown, 8 to 10 minutes.

Melt butter in a small saucepan over medium-low heat. Add heavy cream and cheese. When cheese has melted, add egg yolk. Cook, stirring constantly, until mixture thickens enough to coat the back of a spoon. Remove from heat.

Add Tagliatelle to boiling water, and cook until al dente, following package directions. Drain pasta, and transfer to a large serving platter. Pour sauce over Tagliatelle; sprinkle with mushroom-and-prosciutto mixture. Serve immediately.

This recipe yields 4 servings.

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