Preheat the air fryer to 400°F (200°C).
In a bowl, mix olive oil, garlic powder, paprika, salt, and pepper. Rub this mixture all over the chicken thighs.
Place the chicken thighs in the air fryer basket and cook for 25-30 minutes, flipping halfway through, until the chicken is golden brown and cooked through.
While the chicken is cooking, prepare the herb sauce by combining parsley, tarragon, Dijon mustard, lemon juice, and sour cream in a bowl. Mix well until smooth.
Once the chicken is done, remove it from the air fryer and let it rest for a few minutes before serving.
Serve the chicken hot, drizzled with the French herb sauce.