To prepare the chicken broth (optional- see notes), add the chicken thighs and chicken breasts to a large stockpot. Add approximately 3 quarts of water to the pot and bring to a boil. Cover and reduce heat to low. Simmer for approximately 30-45 minutes.
After the broth has finished simmering and the chicken has finished cooking, remove from heat. Carefully remove the chicken from the broth to a clean cutting board and set aside to rest until cool enough to handle. Strain the broth through a fine mesh strainer into a clean pot to remove any impurities. Shred the chicken.
For the soup
Approximately 15 minutes before you strain the chicken broth, chop and cook the vegetables. Heat one tablespoon olive oil in a large pot or Dutch oven over medium heat. Add the onion and cook, stirring often, for 4-5 minutes or until the onions turn translucent. Add the carrots and celery to the onions and mix well to combine. Continue to cook over medium heat for 10-15 minutes, stirring often. In the last two minutes stir in the minced garlic, mixing well to combine.
Transfer the chicken broth and shredded chicken to the vegetables. Stir in the salt, pepper, and lemon juice and bring to a boil. Reduce heat to low and simmer for 30 minutes or until vegetables are fully cooked.
Cook the noodles separately. As the soup simmers bring a large pot of salted water to a boil and cook pasta according to package instructions. Drain, rinse and toss with olive oil. Set aside.
Add approximately 1/2 cup of the prepared alphabet pasta to each bowl and ladle soup directly on top. Garnish with fresh chopped parsley, if desired.
Cut back on cook time and use store-bought chicken stock (approximately 3 quarts, or 10-12 cups) with shredded rotisserie chicken. Adjust seasoning as needed.