Poach the chicken: place the chicken breasts in a saucepan, cover with water by 2 cm, add 1 teaspoon kosher salt, and bring to a bare simmer over medium heat. Cook for 15-18 minutes until the internal temperature reaches 74°C. Transfer to a plate and shred with two forks. Reserve 480 ml of the poaching liquid as the chicken broth, or use store-bought.