pat the chicken pieces dry and cut any large breasts in half lengthwise so they're less than an inch thick if you haven't done this already
Heat oil in a skillet over medium heat
When oil is hot enough to sizzle, add chicken breasts, and sprinkle with salt and pepper
brown chicken until browned on one side, flip, and saute on the second side until cooked through, thin chicken will cook quickly (Note: cook chicken in batches if skillet is too small to accommodate all of it at once)
Remove chicken from the skillet
Add chicken broth and scrape up any browned bits on the bottom of the pan
Whisk the water and the cornstarch together until smooth
whisk into the chicken broth until smooth
Add milk and stir until the broth has thickened
Stir in sour cream, onion powder, Italian seasoning, and ranch mix until fully mixed
reduce the heat
Add chicken back to skillet and heat through
Garnish with parsley and serve