Combine the cashews and the butter in a food processor. Pulse to a smooth paste. Or, finely chop the cashews and combine them with the butter.
In a medium nonstick frying pan, heat the oil over moderate heat. Season the chicken breasts with 1/4 teaspoon each salt and pepper and add them to the pan. Cook until browned and just done, 4 to 5 minutes per side. Remove the chicken from the pan and let it rest for 5 minutes. Cut into small pieces.
In a large pot of boiling, salted water cook the penne until just done, about 13 minutes. Add the beans during the last 5 minutes of cooking. Drain the pasta and beans and toss with the cashew butter, chicken, and the remaining 1/2 teaspoons of salt and pepper.
Other Nut Butters: Cashews taste delicious in this dish, but you could really use any kind of nut, salted or unsalted, you have on hand. Others you may have on hand that would work: Almonds · Hazelnuts · Peanuts · Pecans · Pistachios · Walnuts
Wine Recommendation: A rich white wine, for example a chardonnay from California or Australia, will go particularly well with the richness of the cashews and butter.