Place a medium saucepan of boiling water on the hob and blanch the baby turnips and carrots. Drain and set aside.
Place a medium frying pan on the heat and add the oil, once hot add the onion petals. Cook for a couple of minutes until the onion colours, remove from the pan and set the onions aside and keep the pan for the fish.
Cook the quinoa in water or soak according to the packet instructions and place in a large glass bowl.
Place the sugar and vinegar in a medium saucepan and heat until the sugar has dissolved. Add the sultanas and onion and warm through until the sultanas have swollen and the onion has wilted. Place the sultanas and onion in the quinoa salad and add the herbs. Season with salt and pepper and the lemon juice.
For the coriander mayonnaise, blend the coriander with 2½ litres/4½ pints water in a blender or a food processor.
Line a colander with a triple-layer of muslin cloth. Place the ice into a large bowl in which the colander will fit.
In a large heavy-based pan, heat the coriander water, whisking continuously. When the temperature reaches 80C/176F the chlorophyll will separate from the water.
Drain the coriander water through the muslin-lined colander, then set the colander into the bowl of ice to chill. Leave until a thick coriander purée is left in the muslin. Scrape this off and reserve for the mayonnaise.
To make the mayonnaise, place the egg yolks, white wine vinegar and mustard into a food processor and blend until pale and creamy.
With the motor running, pour in the oil, in a very thin steady stream, until the mayonnaise thickens.
Add the yuzu juice and coriander purée to the mayonnaise and mix, set aside.
For the crispy onion rings, heat a deep fat fryer to TEMPERATURE? (CAUTION: Hot oil is dangerous. Do not leave unattended.)
Combine the onion rings with the beaten egg in a large bowl and mix well.
Add the flours, ground coriander, fresh coriander and cumin seeds and stir well to combine.
When the oil is hot add a large spoonful of the onion rings and fry for 30-45 seconds, until golden-brown.
Using a slotted spoon, turn over and fry for a further 30 seconds, until crisp and golden-brown all over. Remove with a slotted spoon and set aside to drain on kitchen paper. Season with salt.
Repeat with the remaining onion rings, replenishing the oil in the fryer if it runs low and allowing it to heat up again after a new addition.
Heat a medium frying pan and add the butter. Season the sea bass fillets with salt and freshly ground black pepper.
Fry the sea bass fillets and cook for a couple of minutes on each side.
To serve, place a pool of the coriander mayonnaise on the plate and place the quinoa salad on top. Put the sea bass fillets on top and then some crispy onion rings. Garnish with coriander and basil cress.