Wash the spinach and blanch in salted boiling water until wilted.
Refresh the spinach in iced water and repeat the process for the nettles.
Layer the leaves on a towel to form an oblong shape, roll up, and refrigerate.
Clean the scallops by removing corals and frills, then pat dry.
Debone the sea bass through the belly while keeping fillets attached and removing pin bones.
Place the fish on cling film and top with a layer of leaves and scallops.
Roll the fish into a tight cylinder, wrap in foil, and freeze for 30 minutes.
Remove the foil and slice the roll into 3cm thick pieces.
Remove the cling film, tie each slice with string, and sear in oil and butter.
Cook for 45 seconds per side, then rest for 8 minutes before serving.