Fill a large pot with water and then add the chicken and onion. Cook over medium heat until the pot is brought to a slight boil or simmer, and set the kitchen timer for 4 hours
After 3 hours of cooking time, rinse the celery and carrots and add them to the pot (if you’d like, also add the garlic cloves). Let all of the vegetables cook along with the onion and chicken for the remaining hour
After everything is finished cooking, carefully remove the chicken, onion, and all of the vegetables to a large bowl and let cool slightly before storing in an airtight container in the fridge.
Add your favorite pasta to the pot and let look according to the package directions or until al dente/tender.