Gather the ingredients.

Place the chicken thighs in the Instant Pot, followed by the water, celery, onion, carrots, garlic, parsley, bay leaf, kosher salt, and pepper.

Lock the lid in place and turn the valve to the sealing position. Select the manual setting, high pressure, and set the timer for 35 minutes. When the time is up, let the pressure release naturally for 30 minutes. Carefully release the remaining pressure.

Meanwhile, prepare the matzo ball mixture as the chicken and vegetables are cooking. In a large bowl, whisk the eggs until just slightly beaten. Add the vegetable oil or fat, matzo meal, salt, baking powder, and chopped parsley, if desired. Refrigerate the mixture until you are ready to shape and cook the matzo balls.

With a slotted spoon, remove the chicken thighs and vegetables to a large bowl and set aside. Strain the broth through a fine-mesh strainer, discarding the solids (garlic pieces, leaves, etc.). Pour the broth back into the Instant Pot; set it on sauté and bring to a boil.

With moistened hands, shape the matzo mixture into small balls. You should have 12 to 15 matzo balls.

Drop the matzo balls into the boiling broth. Turn the sauté function to the low setting, 30 minutes. Cover the pot and simmer the matzo balls for 40 minutes. Note: The Instant Pot will automatically turn to the "keep warm" setting after 30 minutes, so cancel the setting at that point and set it to low sauté again for the additional 10 minutes.

As the matzo balls cook, chop the cooked vegetables. Remove the chicken from the bones and discard the skin and bones. Shred the chicken.

Add the chopped vegetables and chicken back to the broth with the matzo balls and heat through.

Add 2 matzo balls to each serving of soup. Sprinkle servings with fresh chopped dill or parsley, if desired.