Cook fettuccini. As the fettuccini is cooking, into a frypan add the mushrooms, bacon and garlic. Add around a tablespoon of mustard more or less as to your taste. Fry until cooked but not crispy.
Add the chicken, cooking but not browning. Better when just cooked as for tenderness.
When ready add the sour cream and add around 1/2 the thickened cream and simmer-around 10-15 minutes.
Taste, if you wish to add more cream then go for it, however it is best to allow the sauce to not thicken too much as it is good when it coats the fettuccini.
Scoop your carbonara on to the fettuccini and add the garlic chives as garnish.