Coarsely crush peppercorns and mix with mustard. Dab meat dry. Remove fat layer and tendon. Rub the meat all around with approx. 2 tsp. salt. Place on an oiled fat pan.
Spread the mustard mixture on the meat. Roast in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for 40-45 minutes. (Then the meat is pink inside. Optimal is the use of a roast thermometer: the core temperature should be 60-65 °C). Remove the roast beef and let it cool down.
Cut the meat into slices for serving. Garnish with parsley.