Method
To make the butter, pour the cream into a bowl and whisk until it starts to thicken then split. Then, use a wooden spoon to beat the cream and drive out the buttermilk. Once the butter granules begin to bind, dip your hands in icy water, then squeeze the butter together to get out as much buttermilk as possible and form a solid mass. Save the buttermilk for soups, smoothies or bread.
In a bowl place the butter with the seaweed flakes, the grated garlic and the salt, add black pepper to season, then beat together. Place the flavoured butter on a sheet of greaseproof paper and form into a rough cylinder. Roll it up in the paper and refrigerate.
Open the scallops, but leave the roe attached to the muscle. Place a scallop in each half shell, remove the butter from the fridge and break a generous disc over the scallop.
Level out the hot embers of the fire with a stick or poker, then place the scallop shells onto them. The scallops will heat up quickly and the butter will start to sizzle, frying the scallops in their own shells. After 1–2 sizzling minutes, flip the scallop meat over without disturbing the shells. Cook for a further 1 minute, until the scallops are cooked through, then remove each shell from the embers. If at any point you think the butter is blackening or bubbling too fiercely before the scallop is cooked, rearrange it in a less hot part of the fire (a little browning is good, though). Set the scallops on plates and tuck in, but remember the shells will be hot!