To a medium bowl, add the chicken broth, condensed soup, dry onion soup mix, and whisk to combine. It's ok if it's not perfectly smooth; set aside momentarily.

To a small bowl, add the dried herbs, salt, pepper, and mix to combine. Rub this mixture into the chicken breasts, making sure to coat them on all sides. Set aside momentarily.

To the slow cooker insert, scatter the diced onions evenly over the bottom, and then sprinkle the garlic over the onions. Toss lightly with a spatula to combine.

Place the chicken breasts on top.

Pour the soup mixture evenly over the chicken.

Place the lid on the slow cooker. Cook on HIGH for about 3-4 hours, or on LOW for about 6-7 hours. Slow Cooking Tips - The exact cooking time will depend on your slow cooker and its heat output. Some are very fierce, some aren't. Chicken is done when it reaches an internal temp of 165F. Use a thermometer and check it, don't guess. Resist the urge to lift the lid and peek on the food "just to check it" because heat and steam will escape, unnecessarily prolonging the overall cook time.

When chicken is done, place it on a cutting board, and use two forks to shred the meat (or if desired, you don't have to shred it and can keep the pieces of chicken intact). Tip - Before getting to work on shredding though, complete the next step with the slurry to start thickening the gravy.

Make a cornstarch slurry by combining 1 tablespoon of cornstarch with 1 tablespoon of water, and stir to combine and dissolve the cornstarch. Add the slurry to the cooking liquid and gravy that's in the slow cooker, and stir to combine. Within a few minutes, the gravy will begin to thicken. Stirring will help accelerate the thickening process. Tip - If your gravy isn't thick enough, you can make 1 more slurry by combining 1 tablespoon of cornstarch with 1 tablespoon of water, add it, stir, and with that your gravy should be sufficiently thick. Gravy will always tighten up when it cools too so if it looks a bit thin now, not to worry, it will thicken as it cools a bit.

Add the shredded chicken back into the slow cooker, toss well to coat it evenly with the gravy and rewarm it slightly. Taste and if desired, add additional salt or pepper.

Optionally garnish with parsley and serve immediately.