Dry the steak and press white and black peppercorns into both sides.
Seal the steak in olive oil over high heat for two minutes per side.
Add half the butter and cook steak for 5-10 minutes, then rest.
Sauté shallots in remaining butter until soft.
Deglaze pan with Worcestershire sauce, brandy, and stock.
Whisk in green peppercorns, mustard, and cream, then season.
Wash and cut potatoes into chunky chips before soaking in water.
Blanch chips in oil heated to 160°C for four minutes, then drain.
Deep fry chips at 190°C for two minutes until golden.
Slice steak on diagonal and stir into the warm sauce.
Serve the sliced steak alongside the hot chips.