For the confit lemon hollandaise sauce, put the caster sugar and 200ml/7fl oz water in a saucepan and bring to the boil. Add the sliced lemons to the syrup and cook on a low heat for about 20 minutes, or until the syrup is glossy and translucent. Leave to cool in the pan.
In a non-reactive pan, heat two tablespoons of the lemon syrup and the white wine vinegar until just boiling Any remaining lemon syrup can be set aside and used for cocktails or other recipes.
Place the egg yolks and a pinch of salt in a food processor. Set the motor to run slowly, then gradually add the hot lemon and vinegar mixture to the egg yolks in a thin stream, until it has all been incorporated into the egg yolks.
With the motor still running, gradually add the melted butter to the mixture in a thin stream, until completely incorporated. Season, to taste, with salt and freshly ground black pepper. Set aside.
For the griddled asparagus, bring a pan of salted water to the boil, add the asparagus spears and cook for 1-2 minutes.
Drain, return the asparagus spears to the pan (off the heat) and drizzle with olive oil. Shake the pan to coat the asparagus spears, then season, to taste, with salt and freshly ground black pepper.
Heat a griddle pan over a medium to high heat. When the pan is smoking, add the seasoned, blanched asparagus and griddle for 3-4 minutes, or until tender. Meanwhile, return the pan to the heat and melt the butter. When the butter is foaming, add the griddled asparagus and shake the pan to coat the asparagus spears in the butter.
For the pan-fried seabass, heat a large frying pan and add the oil. Once hot, add the fish fillets and cook on both sides for 1-2 minutes.
To serve, drizzle a spoonful of sauce on each plate in a circle and place the asparagus on top and the fish on top of that. Drizzle a little more sauce around the plate.