For the steamed sea bream fillets, place two sheets of aluminium foil onto a work surface. Drizzle one tablespoon of olive oil into the middle of each sheet of foil and season with salt and freshly ground black pepper. Place one large basil leaf in the middle of each sheet of foil, then place one sea bream fillet on top. Wrap each sea bream fillet tightly in the foil.
Bring a large pan of water to the boil, then carefully place a steamer on top. Place the wrapped sea bream onto the steamer rack, cover, and steam for 6-7 minutes, or until the fish is cooked through. Remove from the steamer and keep warm.
Preheat the oven to 200C/400F/Gas 6.
For the lemon-roasted new potatoes, bring the fish stock to the boil in a pan with one garlic clove, then add the new potatoes. Reduce the heat until the mixture is simmering and cook for 7-8 minutes, or until the potatoes are tender, then drain well.
Heat one tablespoon of olive oil in an ovenproof frying pan, add the remaining garlic clove and the cooked new potatoes and toss to coat. Add the butter, then add the chopped lemon to the pan. Transfer to the oven and cook for 6-7 minutes, or until the potatoes are golden-brown. Set the potatoes aside to drain on kitchen paper and season with sea salt.
For the asparagus, heat one tablespoon of olive oil a griddle pan until smoking. Add the asparagus, season with salt and freshly ground black pepper, and cook for 1-2 minutes on all sides, or until tender.
For the basil hollandaise, place a heatproof bowl over a pan of simmering water (make sure the bottom of the bowl doesn't touch the surface of the water). Add egg yolks and vinegar and whisk together until smooth and creamy.
Slowly drizzle in the clarified butter in a thin stream, whisking continually, until all of the butter is incorporated and the mixture has thickened and emulsified.
Take the bowl off the heat and season, to taste, with salt and freshly ground black pepper. Fold in the sliced basil.
To serve, spoon the lemon-roasted potatoes onto two serving plates, then lay the asparagus alongside. Unwrap the steamed sea bream and place on top of the asparagus. Squeeze over the lemon juice. Serve with a spoonful of basil hollandaise alongside.