1. Bring 4 litre of water to a boil in a large pot.
2. Meanwhile, shell and devein the shrimp. Slice the mushrooms. Coarsely chop the scallions. Chop the parsley (if using).
3. Add the pasta to the boiling water and cook until al dente, 10 to dozen minutes.
4. Meanwhile, in a large bowl, beat the egg. Stir in the cream, Parmesan, mustard, parsley (if using), anchovy paste (if using), and pepper; set aside.
5. In a large skillet, warm 2 tablespoons of the oil over medium-high heat until hot but not smoking. Add the garlic and mushrooms and stir-fry until the mushrooms are almost limp, about 5 minutes.
6. Add the remaining 1 tablespoon of oil and the shrimp and stir-fry for 2 minutes. add the scallions and stir-fry until the shrimp turn pink and opaque, 1 to 2 minutes longer.
7. Place a colander over a large serving bowl. Drain the pasta into the colander, letting the boiling water heat up the serving bowl. Pour the water out of the serving bowl and add the drained hot pasta. Pour the beaten egg mixture over the hot pasta and toss to cook the eggs as well as to coat the pasta. Add the shrimp-vegetable mixture and toss to evenly distribute. Serve hot. TIMESAVERS: DO-AHEAD: The shrimp can be shelled and deveined ahead. The mushrooms and scallions can be cut up ahead. And the beaten egg mixture can be prepared a short while before cooking. Submitted By JOPETE@ATLAS.ODYSSEE.NET On WED, 10 JAN 1996 082632 -0500