Step 1

Cook fettuccine according to package directions for al dente; drain, reserving 1/2 cup pasta water. Transfer to a serving platter; keep warm.

Step 2

In a large skillet, heat 1 tablespoon oil over medium heat. Sprinkle chicken with salt and pepper. Add to skillet; cook and stir until no longer pink, 4-6 minutes. Remove chicken. Add remaining oil to skillet; stir in next 5 ingredients and saute 4-6 minutes. Return chicken to skillet.

Step 3

Stir in wine and mustard. Bring to a boil; cook until liquid is reduced slightly, 2-4 minutes. Pour chicken mixture over fettuccine; add cheese and tarragon. Toss to combine, adding enough reserved pasta water to moisten pasta. Top with toasted walnuts.