Melt the butter in a pan. Coarsely crush pepper and roast briefly in it while turning. Add the cognac all at once. Bring to the boil. Add beef stock. Let it simmer down to half. Stir cream with starch until smooth, thicken sauce with it. Season with salt, keep warm.
Dab meat dry and cut into 4 medallions of the same size. Season with salt. Heat oil in a pan. Fry the medallions in it vigorously from each side for 3-4 minutes. Remove from the pan and wrap in aluminium foil. Let it rest for about 5 minutes.
Heat the sauce again. Arrange medallions with pepper sauce on plates and garnish with rosemary if desired. French fries taste good with it