In a good size skillet with a tight fitting lid, melt 2 tablespoons of butter on medium heat. when melted, add olive oil and shallots. cook shallots until tender and slightly carmelized. Then add the minced garlic.
Add the mushrooms and mix together until they start to cook down. If the pan appears dry, add a little more olive oil as needed. Cover and Cook until the mushrooms are tender, about 6-7 minutes.
Once the mushrooms are tender, Add the salt, pepper, allspice and sherry. Cook for several minutes until the mushrooms absorb some of the liquid.
Raise the heat a little and add the cream and remaining butter. Stir frequently until the sauce starts to bubble and thicken, then reduce the heat back to medium and add the cheese and parsley, incorporating all ingredients together, adding the cheese gradually. Do not add the cheese all at once or it will not melt properly and clump in the sauce. Add it in about 3-4 additions. Stir until the sauce is thick.
Serve over fettuccine that is cooked al dente.
NOTE- This recipe can easily be halved for a quick romantic dinner for 2!