Place the chicken breast in a bowl and cover with buttermilk, letting it marinate for at least 20 minutes to tenderize.
In a shallow dish, whisk together 2 tablespoons of flour, garlic powder, onion powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting the excess drip off, then dredge thoroughly in the flour mixture.
Heat the avocado oil in a large skillet over medium heat until shimmering.
Carefully place the chicken in the skillet and cook for 5 to 7 minutes per side until the crust is golden brown and the internal temperature reaches 165 degrees.
Transfer the chicken to a plate and set aside, leaving the remaining oil and browned bits in the pan.
Whisk the remaining 1 teaspoon of flour into the pan drippings for 1 minute, then slowly pour in the milk while whisking constantly.
Simmer the gravy for 2 to 3 minutes until thickened, stir in the fresh parsley, and pour over the chicken before serving.