Place the chicken breast between two sheets of parchment paper and pound to an even 1/2-inch thickness, then cut into thick strips.
In a shallow bowl, whisk together the buttermilk with half of the sea salt, black pepper, garlic powder, onion powder, and smoked paprika.
Add the chicken strips to the buttermilk mixture, ensuring they are fully submerged, and marinate in the refrigerator for 30 minutes.
In a separate shallow dish, whisk together 2 tablespoons of whole wheat flour with the remaining spices.
Remove each piece of chicken from the buttermilk, allowing the excess to drip off, and dredge thoroughly in the seasoned flour mixture.
Heat the avocado oil in a large non-stick skillet over medium-high heat until it begins to shimmer.
Carefully place the chicken in the skillet and fry for 4 to 5 minutes per side until the coating is crunchy and the internal temperature reaches 165°F.
Transfer the cooked chicken to a plate and reduce the skillet heat to medium.
Whisk the remaining 1 tablespoon of flour into the residual oil in the pan and cook for 1 minute to create a light roux.
Slowly pour in the milk while whisking constantly, scraping up any browned bits from the pan, until the gravy is thick and creamy.
Drizzle the warm gravy over the crispy chicken and serve immediately.