Cook fettuccini in a pot of salted water (4 qts water, 1 Tbsp salt,) according to package instructions then drain and set aside.

Meanwhile in a large skillet, heat 2 Tbsp olive oil over medium/high heat and sauté chicken until lightly golden and cooked through (5 min). Remove chicken from the pan and cover to keep warm.

In the same pan over medium/high,  add onion, butter and sauté 3 min until soft. Add sliced mushrooms & garlic and sauté until soft (5-7 min), stirring frequently.

Add  cream and simmer over medium/high heat 8-10 min, or until beginning to thicken. Add chicken back to the pan, add chopped parsley and season sauce to taste (1/2 to 1 tsp salt and 1/4 tsp pepper).

Add cooked pasta and stir to combine. Heat another minute until warmed through then turn off the heat, cover and let rest 10-15 minutes then stir and serve garnished with parsley.