For chicken breast meat being added to a stew, I prefer to cook the chicken breasts separately in the oven, then cut or cube the meat and add it to the finished stew to warm, just before serving.
Alternately, if the breasts are skinless and boneless you could poach them in white wine (I almost typed “whine” there). Heat enough wine to cover the chicken in a large skillet. You’ll want it to just barely simmer. Add the chicken breasts and cook until the internal temperature is 160°F (sorry I can’t give you a time, I don’t do this by the clock.)
If you want the chicken to cook mostly in be stew, so it absorbs he flavors, sear the breasts, but don’t cook them through. Then shred or cube them and add it to the the stew. I’ve had great success with this method in my recipe for chicken piquante.