Trying to duplicate a dressing marinated recipe?

My husband brought home the tastiest chicken sub I've ever had, it was simple chicken cubed and marinated in italian dressing, but the dressing is also the sauce. My husband said that he watched them make the sandwich and the chicken was on the stovetop in a covered pot simmering in the dressing. Is that it, could it be that simple?? Anybody ever try this? I bought some dressing and am thawing some chicken hoping to try it, I'm not sure if I should cook the chicken first and then add to the dressing and simmer on the stovetop or what.... help!