Begin by soaking the bone-in, skin-on chicken thighs in buttermilk for at least 30 minutes, or ideally overnight, to enhance moisture and flavor. After marinating, carefully pat the chicken dry using paper towels.

Preheat your oven to 400°F (200°C). Prepare a baking sheet lined with parchment paper or place a wire rack over the sheet.

In a bowl, combine all-purpose flour or cornstarch, garlic powder, onion powder, thyme, salt, and pepper. Coat each dried chicken thigh generously with the mixture.

Place the coated chicken thighs skin-side up on the baking sheet or wire rack. Lightly brush each piece with olive oil or melted Irish butter.

Bake the chicken thighs for 30 to 35 minutes, until golden brown and crispy, and the internal temperature reaches 165°F (74°C).

After baking, allow the chicken to rest for about 5 minutes. Sprinkle with chopped parsley or chives before serving.