Preheat the oven to 200°C/gas mark 6. Line a large baking tray with foil and grease with the oil. Combine the amaranth and garlic powder in a medium bowl and season. Beat the egg in a small bowl and add the flour to another small bowl.
Dip a piece of chicken into the flour. Shake of any access and dip into the egg, allowing any access to drip off. Finally, roll in the amaranth coating and then transfer to the lined baking tray. Repeat with all the chicken pieces.
Transfer the baking tray to the oven. Bake the coated chicken for 25-28 minutes, carefully turning them over halfway, until the chicken is cooked through.
Meanwhile, add the fish sauce, sugar and 6 tbsp water to a small saucepan. Bring to thw boil, then add the ginger and continue to boil until the sauce is slightly thickened. Remove from the heat and leave to cool. Once cool, add the lime juice, tamari, chilli, spring onion and coriander. Stir through.
Once the chicken is ready, serve alongside the sauce for dipping.