Place the chicken breast between two pieces of parchment paper and pound to an even half-inch thickness for uniform cooking.
Place the chicken in a shallow bowl and pour the buttermilk over it, allowing it to soak for at least 15 minutes.
In a separate shallow dish, whisk together 2 tablespoons of the flour, sea salt, black pepper, garlic powder, onion powder, and paprika.
Remove the chicken from the buttermilk, letting excess drip off, then dredge it thoroughly in the flour mixture, pressing to adhere.
Heat avocado oil in a cast-iron skillet over medium heat and pan-fry the chicken for 5 to 6 minutes per side until golden brown and crispy.
Remove the chicken to a plate to rest; whisk the remaining 1 tablespoon of flour into the residual oil in the pan for 1 minute.
Slowly whisk in the milk and chicken broth, simmering and stirring constantly until the gravy thickens into a creamy sauce.
Serve the crispy chicken immediately with the warm gravy poured over the top.