Place boneless, skinless chicken breasts in the slow cooker.
Season chicken breasts with kosher salt, pepper, lemon zest, and sage.
Pour whole milk over the chicken breasts.
Cook on low for one hour, then flip the chicken and cook for another 30 minutes to one hour, or until the internal temperature reaches 165°F.
Enjoy the tender and moist chicken breasts in various recipes throughout the week.
