Hello there. It is wonderful that you are making cost-effective meal preps, and I completely understand your concern about avoiding tough or dry meat.
When cooking boneless, skinless chicken breasts in water, the secret to keeping them tender is avoiding a hard, continuous boil. High heat causes muscle fibers to contract tightly, which results in a rubbery texture. Once your water reaches a rolling boil, add your chicken breasts, reduce the heat to a low simmer, and cover the pot with a lid.
For standard medium-sized chicken breasts weighing around 6 to 8 ounces, they will typically need about 12 to 15 minutes in gently simmering water to cook through completely. If the breasts are particularly large or thick, it may take closer to 15 to 20 minutes.
To be completely certain your chicken is safe and perfectly cooked, I strongly recommend using a digital meat thermometer. Insert it into the thickest part of the breast; once it reaches an internal temperature of 165 degrees Fahrenheit, it is ready to be removed from the pot. Be sure to let the meat rest for 5 minutes on a cutting board before cutting or shredding so the juices redistribute nicely.
