Preheat the oven to 180°C. Season the beef with salt and freshly ground pepper. Heat the vegetable oil until almost smoking in a heavy-based pan. Add the beef and cook for 3 minutes. Turn the beef and cook for a further 3 minutes until the meat is evenly browned. Remove the beef from the pan and allow to rest in a warm place whilst the remainder of the dish is prepared.
Heat two heavy-based pans and add 40ml olive oil to each. When hot, add the mushrooms to one pan and the truffle gnocchi to the other and sauté both for 3 - 4 minutes until golden brown. Season to taste with salt and freshly ground pepper. Add 20g butter to each pan and toss through the mushrooms and gnocchi until melted. Drain well and mix together in a bowl, keeping them warm.
In a large heavy-based pan heat the remaining 40g butter until foaming. Add the asparagus and sauté in the butter allowing them to take on a little colour. Season to taste with salt and freshly ground pepper and drain well.
Place 3 asparagus spears onto a warm plate and spoon the truffle hollandaise over the spears leaving the tips exposed. Garnish with 3 sprigs of chervil. Spoon the mushrooms and gnocchi beside the asparagus and place a piece of beef on top of them. Spoon the sauce Perigeux over and around the beef.