Prepare the chicken. If your chicken breasts are very thick, you can pound them slightly to an even thickness (about 2cm or 0.75 inches) for more uniform cooking. This can be done by placing the chicken between two sheets of plastic wrap or parchment paper and gently pounding with a meat mallet or the bottom of a heavy pan.

Season the chicken. In a small bowl, combine the ranch seasoning mix, salt, and black pepper. Pat the chicken breasts dry with paper towels. Rub the seasoning mixture evenly over all sides of the chicken breasts, ensuring they are well coated.

Heat the pan. Place a large skillet over medium-high heat. Add the olive oil and let it heat up until it shimmers.

Sear the chicken. Carefully place the seasoned chicken breasts into the hot skillet. Sear for about 5-7 minutes per side, until golden brown and nicely crusted.

Finish cooking. Reduce the heat to medium-low. Cover the skillet and continue to cook for another 8-12 minutes, or until the chicken is cooked through and the internal temperature reaches 74°C (165°F) when checked with a meat thermometer. Cooking time will vary depending on the thickness of the chicken breasts.

Rest and serve. Remove the chicken from the skillet and let it rest on a cutting board for at least 5 minutes before slicing or serving. This allows the juices to redistribute, ensuring a more tender and moist chicken.