In a small bowl whisk together the olive oil, fresh lemon juice, salt and fresh ground black pepper. Set aside.
Cook the Orzo according to package directions. Drain. Keep warm. Set aside.
Wipe off the chicken with a wet paper towel. Chop. Sauté the chopped chicken in the olive oil and butter until cooked through about 4 min. Keep warm. Set aside.
In a medium size bowl add: cooked orzo, onion, dill, parsley, tomatoes, cheese, and nuts if using. Mix in the warm chicken and arugula. Toss with the dressing and serve immediately.