Bring a large pot of salted water to a boil. Add the pasta, stir, and cook for 7 minutes. Drain and return the pasta to the pot, toss with olive oil.
Meanwhile, heat the chicken stock in a large stock pot over medium heat. Bring to a simmer, add the chicken breasts, and poach until cooked through, 8-10 minutes. Transfer the chicken to a plate and shred with two forks or your hands.
Add the onion, carrot and celery to the chicken broth, cover, and cook until tender, about 10 minutes. Stir in the chicken and pasta. Season with salt and pepper.
Divide the soup between bowls and garnish with dill.