Dice 1 large onion (about 2 cups). Peel and cut 3 medium carrots crosswise into ½-inch thick rounds (about 1 ¾ cups). Cut 3 medium celery stalks crosswise into ½-inch thick pieces (about 1 ¼ cups). Mince 3 garlic cloves.

Melt 2 tablespoons unsalted butter or heat 2 tablespoons olive oil in a Dutch oven over medium heat. Add the onion mixture, 2 ½ teaspoons kosher salt, and ½ teaspoon black pepper. Cook until the onion is translucent, about 5 minutes.

Add 64 ounces low-sodium chicken broth, 5 sprigs fresh thyme, and 2 dried bay leaves. Increase heat to medium-high and bring to a boil. Meanwhile, shred the meat from the rotisserie chicken into bite-sized pieces.

Add the chicken and 6 ounces dried extra-wide egg noodles to the soup. Reduce heat and cook until noodles are just shy of al dente, about 6 to 7 minutes.

Remove and discard thyme sprigs and bay leaves. Taste and season with more kosher salt as needed. Add chopped parsley or dill. If using, squeeze juice from ½ large lemon into the soup.