Preheat a deep-fat fryer to 160C/325F (CAUTION: Hot oil can be dangerous. Do not leave unattended.) Dust the sea bass portions with rice flour and set aside.
For the batter, mix together the flours and baking powder in a large bowl. Whisk in the sparkling water to make a smooth batter. Then stir through the chilli, coriander and sea salt. Set aside until ready to cook the fish.
For the chips, cut the potatoes into fairly thin chips. In a large pan of boiling water, cook the chips until just soft, but not breaking up (approximately two minutes). Remove from the pan and drain thoroughly.
Add the chips to the deep-fat fryer and cook until they are light golden-brown (approximately two minutes). Drain on kitchen paper and set aside (ready for a second frying just before serving).
For the samphire, bring a pan of salted water to the boil. Add the samphire and cook for a few minutes. Immediately drain and coat with butter and balsamic vinegar. Season with salt, pepper and a pinch of sugar.
For the sauce gribiche, first make a mayonnaise by placing the whole egg into a food processor along with the Dijon mustard, salt and pepper. Blend until smooth and, with the motor running, add the rapeseed oil in a thin stream until the mixture starts to thicken. Then add the lemon juice and white wine vinegar. Keep adding the oil until you have a smooth emulsion with a mayonnaise consistency.
Spoon the mayonnaise into a bowl and add the chopped hard-boiled eggs, cornichons, capers, herbs and sugar. Mix well and set aside.
To cook the bass, dredge the fillets in the batter and place them into the deep-fat fryer. Cook for 5-10 minutes, or until the batter is crisp and golden-brown.
Just before serving, fry the chips for a final time until crisp and a deep golden-brown.
To serve, place the fried bass and chips on plates with the samphire and gribiche.