Mash the boiled potatoes with butter and oil in a large bowl and season with salt and pepper.
Heat olive oil and butter in a frying pan and fry the garlic and onion for 4 minutes until golden.
Pour in the red wine and simmer until the liquid reduces by half.
Add beef stock and simmer until thickened, then adjust seasoning with salt and pepper.
Rub the liver with olive oil and season both sides with salt and pepper.
Chargrill the liver in a smoking hot griddle pan for 4 minutes on each side.
Rest the liver on a warm plate for 1 minute.
Serve the liver on top of the mash, cover with gravy, and garnish with chopped chives.