In a large bowl, combine the buttermilk, paprika, garlic powder, and salt. Add the chicken thighs and mix well to coat. Let rest for at least 30 minutes, or refrigerate overnight for deeper flavor.
In a separate bowl, mix together the flour and cornstarch. Remove the chicken from the buttermilk mixture, letting any excess liquid drip off. Dredge the chicken in the flour mixture, shaking off excess.
Heat the avocado oil in a large skillet to 350°F / 175°C — test with a wooden spoon, bubbles should form immediately. Fry the chicken for 5-6 minutes per side, or until the coating is deep golden brown and pulls away from the pan cleanly.
Check with a meat thermometer — chicken is done at 165°F / 74°C at the thickest part. Rest on a wire rack for 5 minutes before serving — this redistributes the juices and keeps the coating from going soggy.
Serve hot and enjoy!