Freshly grated Parmesan for garnish
In a heavy pot melt and butter and olive oil and saute the shallot and garlic for a few minutes.
Add in the mushrooms and saute, stirring often, for about 5 to 8 minutes, until the mushrooms just tender. If the pot seems too dry, add a little more olive oil.
Add the Marsala into the hot pot and let it evaporate for a minute, then add the chicken stock, thyme, lemon juice, salt and pepper.
Let the sauce simmer and reduce for a few minutes. Sprinkle in a dash of cornstarch (blended with water) and blend in.
Add in the cream, and bring back to a simmer. Check for seasoning and set aside while you cook the fettuccine.
When the fettuccine is just al dente, either add it to the sauce and toss well, or put it in a serving bowl and top with the sauce. Garnish with cheese and parsley.