1. **Prepare the sauce**: In a small mixing bowl, combine the cream of chicken soup, milk, and ranch dressing mix. Whisk until smooth and well combined.
2. **Layer the ingredients**: Place the chicken breasts, carrots, and potatoes in the slow cooker. Pour the prepared sauce over the top, ensuring all ingredients are coated.
3. **Cook**: Cover and cook on low for 6 to 8 hours, or on high for 3 to 4 hours, until the chicken is tender and cooked through.
4. **Shred chicken (optional)**: If you prefer shredded chicken, remove the chicken breasts, shred them, and return them to the slow cooker. Stir to combine with the vegetables and sauce.
5. **Fix separated sauce**: If the sauce separates, simply remove the chicken and vegetables, whisk the sauce to combine, and then add everything back to the slow cooker.