Cut the chicken in bite size pieces. In a small bowl, combine the ranch seasoning mix, salt and pepper. Sprinkle the seasoning mixture evenly over both sides of the chicken breasts, ensuring they are well-coated.
In a large skillet or sauté pan, heat 2 tablespoons olive oil over medium-high heat. Add the seasoned chicken pieces to the pan in a single layer, avoiding overcrowding. Sear for 5-6 minutes, stirring occasionally, until the chicken is golden brown and cooked through. Remove the chicken from the pan and set it aside.
Alternate Method: If you prefer, you can season the whole chicken breasts first, sear them on both sides until golden brown (about 3-4 minutes per side), let them rest for 5 minutes, and then cut them into bite-sized pieces. This method also works well and can help retain more juices within the chicken.
In the same skillet, reduce the heat to medium and add 3 tablespoons butter. Once melted, add the minced garlic and sauté for 1 minute until fragrant.
Stir in the cream of chicken soup, 1 cup milk, and 1 packet ranch seasoning mix. Mix well until smooth and creamy. Bring the mixture to a gentle simmer, stirring frequently.
Return the chicken to the skillet, and mix into the gravy. Reduce the heat to low, cover the skillet, and let it simmer for 15 minutes. The chicken should be cooked through and tender.
Stir in ½ cup sour cream until the gravy is smooth and creamy. Stir until the sour cream is well incorporated.
Garnish with some fresh parsley or green onions and serve with mashed potatoes or rice.