Pound the white peppercorns, garlic, and cilantro root together using a mortar and pestle. Transfer the mixture to a mixing bowl.

Add the soy sauce, erythritol, and fish sauce to the bowl with the pounded mixture. Stir until the erythritol dissolves.

Add the chicken leg quarter to the bowl and coat it well with the marinade. Let it marinate for 1 hour.

After marinating, bake the chicken in an air fryer or convection oven at 480°F (250°C) for 30-40 minutes. Check to make sure the chicken is cooked through. Once done, serve on a plate and enjoy.