To make the mash, place the potato, butter and oil in a large bowl. Season, to taste, with salt and freshly ground black pepper and mash to your preferred consistency.
To make the gravy, heat the olive oil with the butter in a frying pan over a medium heat. Add the garlic and onion and fry for 3-4 minutes, until golden.
Add the red wine and simmer until the volume is reduced by half.
Add the beef stock and simmer to reduce again, until the gravy is thickened, then season, to taste, with salt and freshly ground black pepper.
For the calf's liver, rub the calf's liver with the olive oil then season both sides with salt and freshly ground black pepper.
Heat a griddle pan until smoking. Add the liver and chargrill for four minutes on each side, until cooked through, then rest for one minute on a warm plate.
To serve, place the mash in the centre of a warm plate. Place the liver on top of the mash, spoon over the gravy and sprinkle over with fresh chopped chives.