Preheat the oven to 600 degrees F.
Brush the steak with butter and then sprinkle with 2 tablespoons of the pepper and the salt. Heat a medium pan with oil until just smoking. Cook until a nice crust forms on the bottom of the steak and then flip, about 3 minutes on each side. While the steak is cooking, add a spoonful of butter to the pan and baste the steak for 1 to 2 minutes. Transfer the steak to a clean ovenproof pan and cook in the oven for 5 to 7 minutes. Rest the steak while you cook the sauce.
Toast the remaining 1 teaspoon black pepper and the green peppercorns in a dry medium pan. Deglaze with the brandy and reduce by half. Add the mustard and reduce by half. Add the cream and reduce by half. Add the veal demi-glace and pour over the steak. Serve the steak with French fries.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.