How to Make It
In a large nonstick frying pan, heat 1 tablespoon of the oil over moderately high heat. Season the chicken with 1/4 teaspoon each of the salt and pepper. Sauté until just cooked through, 2 to 3 minutes. Remove from the pan.
Remove any tough stems from the spinach. In the same pan used for the chicken, heat the remaining 1 tablespoon oil over moderate heat. Add the garlic and mushrooms and cook, stirring, for 2 minutes. Add the spinach, let it wilt, and stir in 1/2 teaspoon of the salt and the remaining 1/4 teaspoon pepper. Simmer for 2 minutes. Add the zest, orange juice, and chicken broth. Simmer for 2 minutes and then add the cream, the chicken, and the remaining 1/2 teaspoon salt. Remove from the heat.
In a large pot of boiling, salted water, cook the fettuccine until just done, about 12 minutes. Drain the pasta and toss with the chicken and sauce.