Preheat the oven to 60°C.
Brown the beef in 15ml vegetable oil for 2 minutes and allow to cool.
Wrap the beef in heatproof clingfilm and roast for 30 minutes.
Ensure the beef core temperature reaches 57-59°C.
Sear the beef in hot oil and butter for 30 seconds per side.
Sweat shallots and thyme in butter then reduce Madeira by half.
Add red wine, reduce by two-thirds, then add stock and boil.
Reduce the liquid again by two-thirds and whisk in butter and seasoning.
Sauté button onions and mushrooms in butter then stir in chervil.
Preheat the oven to 180°C for the mash ingredients.
Roast olive-oil drizzled smoked garlic for 25 minutes until soft.
Boil potatoes for 18 minutes, drain, and dry over heat.
Mash potatoes with the roasted garlic flesh, olive oil, and cream.
Serve beef slices over mushrooms with mash and Madeira jus.