Step 1

Prepare the following, adding each to the same medium bowl as you complete it: Dice 1 medium yellow onion (about 1 1/2 cups). Peel and halve 2 medium carrots lengthwise, then cut crosswise into 1/4-inch pieces (about 1 cup). Cut 2 medium celery stalks crosswise into 1/4-inch pieces (about 1 cup). Finely chop 3 garlic cloves.

Step 2

Melt 3 tablespoons unsalted butter in a Dutch oven or large pot over medium heat. Add the onion mixture, 3/4 teaspoon dried thyme, 1 dried bay leaf, 1 teaspoon of the kosher salt, and 1/4 teaspoon black pepper. Cook, stirring occasionally, until the onion is softened and translucent, about 5 minutes.

Step 3

Meanwhile, season 1 1/2 pounds boneless, skinless chicken breasts or thighs all over with the remaining 1 teaspoon of the kosher salt. (If using thick chicken breasts, start at the thickest end and hold your knife parallel to the cutting board, then cut the chicken breasts in half - also known as butterflying).

Step 4

Sprinkle 1/3 cup all-purpose flour into the pot and cook, stirring constantly, for 1 minute to cook the floury taste out. While stirring constantly, pour in 1 (32-ounce) carton low-sodium chicken broth and 2 cups whole or 2% milk. Add the chicken in a single layer. Increase the heat to medium-high and bring to a lively simmer, stirring occasionally.

Step 5

Reduce the heat as needed to maintain a gentle simmer. Cook, stirring and scraping the bottom of the pot occasionally until the chicken is cooked through, and an instant-read thermometer inserted into the thickest part of the chicken registers at least 165°F, about 10 minutes for thighs or 12 to 20 minutes for breasts. Meanwhile, juice 1 medium lemon (about 1/4 cup). Pick the leaves from 8 to 10 fresh parsley sprigs until you have 2 tablespoons and finely chop.

Step 6

Using tongs, transfer the chicken to a clean cutting board. Add 1 cup frozen peas to the soup and stir to combine. Use two forks to shred the chicken or cut into bite-size pieces.

Step 7

Remove the pot from the heat. Remove and discard the bay leaf. Return the chicken to the soup, add the lemon juice, and stir to combine. Taste and season with more kosher salt and black pepper as needed. Garnish with the parsley.