Add the garlic and onion ... 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 ...
Take the pan off the heat and keep the onions warm. Heat a grill or a griddle pan to high and cook the bacon until crisp at the edges. Keep it warm. Season the liver slices with salt and pepper ...