Restaurants make chicken breasts so tender by marinating, brining and precise cooking methods as well as using high quality chicken.
Brining the chicken breasts involves soaking the chicken breasts in a salt solution, which helps to break down the proteins and retain moisture.
Marinating the chicken breasts using oil, acid and spices also further tenderizes the meat and adds flavor.
Also the use of proper cooking methods for the chicken breasts which include grilling, roasting or even sous vide, along with careful temperature control, also help to prevent dryness and overcooking of the chicken breasts which can make for tough chicken breasts if it's overcooked and dried out.
Velveting which is another method of making meats including chicken breasts tender is a Chinese cooking technique which means to marinate strips of meat with egg white and cornstarch, then dipping then in a hot oil bath before finally stir-frying them, the meat develops a texture that is tender, silky, and smooth.
Preparing velvet meat is a staple technique in Chinese cuisine that allows home cooks to tenderize tough, chewy cuts before stir-frying them over high heat in a wok.
It is worth the effort and work and time to Tenderize meat that is very tough as it makes the meat easier to chew and digest.
But if the meats are soft enough already then it may not be worth the effort of Tenderizing the meat.
Any meat that is tough I always take the time and Tenderize it but if the meat is a softer meat already then I do not take the time to Tenderize it.
When you Tenderize meat with a meat tenderizing mallet it softens the meats fibers.
When the meats fibers are softened it makes the meat easier to chew and to digest.
Tenderizing meat is done by using a meat tenderizing mallet and it's like a hammer but for meat and you pound the meat by working back and forth around the meat and flipping the meat over and making sure to pound the meat on both sides for a few minutes.
Then when done you cook it like normal and it will be much more tender and easier to chew the meat.