Peel the russet potato and cut into 1-inch cubes.
Place potato cubes in a pot of salted water, bring to a boil, and cook for 12-15 minutes until tender.
While potatoes boil, mince the garlic cloves and finely chop the rosemary and thyme.
Season the chicken breast with half of the salt, pepper, and chopped herbs.
Heat a skillet over medium-high heat and sear the chicken for 6-7 minutes per side until the internal temperature reaches 165°F.
Drain the potatoes and return them to the pot.
Add the ghee, Greek yogurt, minced garlic, remaining herbs, salt, pepper, and chicken broth to the potatoes.
Mash the potatoes until smooth and velvety.
Slice the chicken and serve it over the warm mashed potatoes.