For the hazelnut butter, toast the hazelnuts in a dry frying pan for 1–2 minutes until golden, then sprinkle with the sugar and cook for another minute. Transfer the nuts to a food processor and blitz until finely ground. Tip the nuts onto a plate and leave to cool slightly.
While the hazelnuts are still slightly warm, mix them in a bowl with the butter and chopped herbs. Season with salt and pepper. Spoon the hazelnut butter onto a sheet of baking paper and form into a long sausage shape.
Place another sheet of baking paper on top and roll to form an even log. Chill in the freezer for 1 hour until firm. (There will be more hazelnut butter than you need – it can be frozen for future use).
For the garnish, bring a saucepan of salted water to the boil. Add the asparagus and blanch for 2 minutes, then add the samphire to the pan for 10 seconds. Drain and refresh the vegetable in a bowl of ice-cold water. Drain again and set aside in a bowl.
Preheat the oven to 220C/200C Fan/Gas 7 and grease a baking tray. Slice 12 rounds of hazelnut butter, about the thickness of a £1 coin, and set aside.
For the smoked butter hollandaise, melt the smoked butter in a small saucepan over a medium heat until it begins to bubble. Remove from the heat and leave to cool until tepid.
Meanwhile, put the egg yolks and lemon juice into a large heatproof bowl set over a saucepan of simmering water, making sure the base of the bowl does not touch the water. Whisk with a handheld mixer until it thickens enough to leave a ribbon trail when you lift the beaters from the bowl. Remove the bowl from the pan. Slowly add the tepid butter, whisking constantly until it is all incorporated. Season with the cayenne and salt to taste and add a little more lemon juice if needed. Keep warm.
For the scallops, place a frying pan over a medium–high heat. Add 1 tablespoon of olive oil to the pan and season the scallops with sea salt. When the oil is hot, carefully lay the scallops in the pan, placing the side of the scallop down that would have been against the flat shell. Cook the scallops for 1½–2 minutes until golden on the underside. Immediately remove the scallops from the pan using a palette knife and transfer to the baking tray, golden side up. Lay a slice of hazelnut butter on each scallop and place in the oven. Cook for 2–3 minutes, depending on their size.
Meanwhile, place the asparagus and samphire on a separate baking tray, drizzle with the oil and season with salt and pepper. Warm through in the oven for a few minutes.
To serve, place the asparagus on warmed plates and spoon over the hollandaise. Top with the scallops, scatter over the samphire and serve immediately.