Set your Instant Pot to sauté mode, add a splash of oil, and cook the chopped onions until they turn translucent and fragrant, about 3 minutes.
Add the sliced carrots and diced celery to the pot, stirring for another 2 minutes until the vegetables soften slightly and release their aroma.
Pour in the chicken broth, then place the bay leaf into the liquid. Season with salt and pepper to your taste, stirring gently to combine.
Arrange the chicken breasts on top of the vegetables, pressing them slightly into the broth.
Secure the lid on the Instant Pot, set it to high pressure, and cook for 10 minutes. Once the cooking cycle ends, carefully perform a quick release to release the steam.
Open the lid carefully, and check that the chicken is cooked through and shreds easily with a fork. Remove the chicken breasts and set aside to cool slightly.
While the chicken cools a bit, stir the soup and discard the bay leaf. Shred the chicken into bite-sized pieces using two forks.
Return the shredded chicken to the soup, stir well, and allow it to heat through for another minute or two.
Squeeze fresh lemon juice into the soup for brightness, then taste and adjust seasoning with salt and pepper as needed.
Ladle the hot, flavorful soup into bowls, garnish with a slice of lemon or fresh herbs if desired, and enjoy this comforting, nourishing meal.
