For the scallops and black pudding, preheat the oven to 170C/340F/Gas 3.
Remove the casing from the black pudding and chop the pudding into slices.
Place the black pudding on a roasting tray and bake in the oven for 10-12 minutes.
Meanwhile, heat a frying pan until hot and add the olive oil. Add the scallops and cook for 1½-2 minutes on each side.
For the mash, place the celery, potato and apple into a saucepan and cover with water.
Bring to the boil and cook until tender.
Drain and mash with a potato masher or pass through a potato ricer.
Season, to taste, with salt and freshly ground black pepper. Add the nutmeg and some butter if you like, and stir to combine.
To serve, spoon three tablespoons of the mash onto each serving plate, about 5cm/2in apart. Place a scallop on top, then top with a small pile of the cooked black pudding.
Garnish with a sprig of fresh chervil and squeeze a little lemon juice over. Season with more salt and freshly ground black pepper. Serve.
