How to Make It
In a large nonstick frying pan, toast the walnuts over moderate heat, stirring, until lightly browned, about 5 minutes. Remove the nuts from the pan and chop.
In the same pan, heat 2 tablespoons of the oil over moderate heat. Season the chicken breasts with 1/8 teaspoon each salt and pepper. Cook the breasts until browned and just done, 4 to 5 minutes per side. Remove the chicken from the pan and let rest for 5 minutes before cutting the meat into chunks.
In a medium glass or stainless-steel bowl, combine the remaining 6 tablespoons oil, the vinegar, 3/4 teaspoon salt, and 1/4 teaspoon pepper. Add the chicken.
In a large pot of boiling, salted water, cook the bow ties until just done, about 15 minutes. Drain the pasta and toss it with the walnuts, the chicken-and-vinaigrette mixture, and the watercress. Serve warm.