Remove sinews and excess fat from the beef and cut pieces 2 cm x 2cm x 1cm.
Remove the rind from the bacon and cut into 2cm dice (lardons).
Heat the oil in a pan and sear the meat until brown on all sides.
Add the demi-glace and red wine and cover with a lid. Simmer gently for approximately 2 - 2½ hours.
Blanch the onions and lardons in boiling water.
Fry the bacon (lardons) in a little oil. Add the mushrooms and onions, sprinkle with a pinch of sugar and sauté until cooked, season with salt and pepper.
Serve the beef accompanied by the garnish.
