Preheat a grill. Drizzle the chicken with oil and season with salt, pepper, and essence. Place on the grill and cook until cooked through, about 4 minutes on the first side, and 5 minutes on the second side. Remove the chicken from the grill and cut into cubes.
In a food processor, combine the arugula, parsley, walnuts, garlic, cheese, lemon juice, salt, and pepper, and process on high speed until the greens are finely chopped. With the machine running, add the extra-virgin olive oil and 1/4 cup of the olive oil in a steady stream and process until smooth.
Bring a large pot of salted water to a boil. Add the pasta and cook until al dente. Drain the pasta and shock in an ice bath and place in a bowl. Toss with some olive oil so it doesn't stick.
Toss the pasta with the arugula pesto, to taste. Let cool, cover with plastic wrap, and refrigerate until well chilled. Toss the cubed chicken, red and yellow tomatoes, feta, and olives to the pasta, and toss to combine. Adjust the seasoning, to taste, and serve, garnished with baby arugula.
Yield: 8 to 10 servings