Chicken Pasta Salad

In a large pot of salted boiling water, cook fusilli according to package directions until al dente. Drain and transfer to large bowl.  Season chicken breasts with garlic powder, salt, and pepper. In a large skillet over medium heat, heat oil. Cook chicken until golden and cooked through, 8 minutes per side. Let rest 10 minutes, then cut into 1" pieces. Meanwhile, make dressing: In a medium bowl, whisk together oil, vinegar, Italian seasoning, garlic, and mustard. Season with salt and pepper. In the large bowl with the pasta, toss together all remaining ingredients. Pour dressing over salad, toss until coated, and serve.