Preheat the oven to 200C/400F/Gas 6.
Wrap each chicken liver in a rasher of bacon.
Rub the wraps with the vegetable oil and season well with salt and freshly ground black pepper.
Place into a hot ovenproof frying pan and fry for one minute on each side, until golden-brown. Transfer to the oven and roast for 8-10 minutes, or until the livers are completely cooked through.
Heat the olive oil in a frying pan and fry the onion and garlic for 2-3 minutes, until softened.
Add the mushrooms and fry for 2-3 minutes.
To serve, place the mushroom mixture onto a warm plate. Place the bacon-wrapped liver onto the mushrooms and garnish with the parsley leaf.