Pre- and make: about half an hour, roast: 20-half hour.
Remove the meat from the refrigerator about 1 hour before frying.
Meanwhile, prepare the sauce: Heat butter in a frying pan. Sauté shallot, pepper briefly. Add stock and wine, bring to the boil, simmer liquid to about 3 tablespoons (for an initial quantity of 3 dl red wine), strain, set aside.
Stir oil with salt, paprika and pepper, put half of it into a sufficiently large bowl, mix potatoes with it.
Stir mustard through with remaining spiced oil, brush meat with it. Insert meat thermometer in the thickest part of the roast (fat side up).
Heat clarified butter in a small roasting pan until hot. Heat the tray in the lower half of the oven heated to 240 degrees for about 2 minutes. Take out, put meat on it, pour hot clarified butter over it. Add potatoes. Roast: 10 min. in the lower half of the heated oven.
Reduce temperature to 180 degrees, continue roasting for about 10-20 min (depending on the thickness of the meat). The core temperature of the meat should be 60 degrees. Remove roast beef from the stove, stand with the lid closed for about 10 min. before carving.
Finish roasting potatoes in turned off stove for about 10 min, preheat plate.
Finish cooking the pepper sauce: Pour prepared sauce back into frying pan. Allow liquid to bubble up, remove frying pan from heat.