For the Madeira reduction, heat a frying pan over a medium heat and add the butter. When the butter is foaming, add the lardons and shallot. Fry for 3-4 minutes, or until the lardons and shallots are golden-brown.
Add the Madeira and carefully tip the pan towards the flame of the hob, so that the alcohol catches alight. When the flame has gone out, cook until the liquid has reduced in volume by three-quarters.
Add the beef stock, stirring well, and cook for 3-4 minutes, or until reduced in volume by half. Then season, to taste, with salt and freshly ground black pepper. Stir in the chervil.
For the mash potatoes, cook the potatoes in a pan of boiling salted water for 12-15 minutes, or until tender. Drain.
Push the potato through a potato ricer into a saucepan. Alternatively, mash with a potato masher, but the finish will be less smooth. Return to the heat, then add the butter and cream and beat to a smooth purée. Season, to taste, with salt and freshly ground black pepper. Place in a piping bag and set aside.
For the calves’ liver, season the livers, to taste, with salt and freshly ground black pepper.
Heat a large frying pan over a high heat and the butter. When the butter is foaming, add the livers and fry on both sides for 1-2 minutes, or until golden-brown all over but still slightly pink in the middle. Remove from the pan and set aside to rest.
For the cavolo nero and wild garlic, add the butter to a hot frying pan and, once hot, add the cavelo nero and cook for a minute. Add the wild garlic and cook for a further two minutes, then season with salt and pepper.
To serve, pipe the mash into four shallow bowls and place the liver and cavolo nero and garlic by the side, and pour over the sauce.