Carbonara became a classic Italian dish during World War II when the Italians discovered that American servicemen liked eggs and bacon. Using thick-cut bacon simulates the texture of pancetta but gives the sauce a better flavor.
In a separate saucepan, place butter and olive oil. Heat until the butter is frothy, then add the shallots and mushrooms. Saute until the mushrooms are browned on the edges and have given up some of their water.
Cook bacon till crisp and chop into small pieces. The microwave works well for this. Do not throw away bacon fat.
Put the cut bacon and some of the fat in a saute pan and saute the mushrooms until they have nicely browned. Set the mixture aside.
In a large pot, boil water and cook pasta until al dente. Drain pasta and reserve.
Put bacon fat into the pot where pasta was cooked. Add sour cream and mix well. Add egg and mix thoroughly. You should have a nice yellow sauce at this time.
Add the mushroom mixture and the bacon, and mix. Finally, add the pasta and toss to coat.
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