For the sole, preheat the oven to 230C/450F/Gas 8.
Ask your fishmonger to remove the dark skin from the megrim. You can do it yourself by cutting into the tail of the fish at an angle and gently scraping back the skin. With a dry kitchen towel pull the skin from the tail towards the head, it should all pull away.
Cut the head off and using sharp scissors, cut around the edge of the fish and remove the fins. Wash the fish and pat dry.
Sprinkle the flour onto a plate and season with salt and freshly ground black pepper.
Dust the fish in the flour on each side.
Heat a non-stick ovenproof frying pan on a high heat and pour in the vegetable oil.
Place the fish in the pan, white skin-side down, and fry for 2-3 minutes, or until pale golden-brown. Turn the fish over using a palette knife.
Add a knob of butter and place in the oven to cook for 6-7 minutes.
Meanwhile, for the shrimp butter, cook the sea kale in a pan of salted boiling water for 2-3 minutes, or until tender. Drain and refresh in iced water, then drain once more and pat dry.
Peel the lemon, remove the pith by gently scraping with a knife (try not to pierce the flesh of the lemon) and slice into rounds (these are your lemon flowers.)
Heat a frying pan until hot, add the butter and shallot and fry for 2-3 minutes. Add the mace, cayenne pepper and Gentlemen’s relish and stir until well combined. Add the shrimps and sea kale, remove the pan from the heat and keep warm.
Season with salt and freshly ground black pepper and a squeeze of lemon juice.
To serve, place the sole in the centre of a large serving plate. Spoon over the shrimp mixture, criss-crossing the batons of sea kale over the top of the fish. Squeeze in two slices of lemon, then sprinkle with pea shoots.