Partially cover the soup with a 1-inch gap and bring to a simmer over high heat, then reduce to a gentle simmer over medium-low or low if your stove runs hot. Simmer until the chicken shreds easily with two forks, about 15-20 minutes. You can make the Tortilla Strips (instructions below) while the soup simmers. Remove the chicken and let rest 5 minutes before shredding. Meanwhile...