You are surely thinking this is certainly an exageration and there is no such thing as one miraculous breathing technique. Oh well, you don't need to believe me but maybe you will believe Andrew Huberman Ph.D., neuroscientist and tenured professor in the department of neurobiology, psychiatry and behavioral sciences at Stanford School of Medicine. He wanted to find out which was the most effective technique with which people would benefit the most in only 5 minutes.
He compared 4 techniques: 1) meditation 2) box breathing 3) sigh and 4) hyperventilation and came to the conclusion that what he calls "physiological sigh" is the one that has the most positive impact to relief stress in the body, even after 1 breath only.
You can listen to him explaining the study on this super interesting podcast episode with Dr. Sara Gottfried on Youtube from minute 57'.
You can also see this shorter video where he explains only how to sigh.
Let me know how it goes and happy SIGHing.