Grind half onion, sauté in the pan with 3-4 tablespoons of extra virgin olive oil a few minutes, then incorporate the brandy and the green peppercorns.
Boil a couple of minutes to evaporate the alcohol, add the cream. Cook 2 or 3 minutes and remove half of the peppers. Grind the rest of the sauce with the mixer. Pour into a saucepan incorporating the peppers we had removed.
In a frying pan, add extra virgin olive oil and with the medium-low heat fry the sliced potatoes, the chili peppers and the rest of the sliced onion until they are tender but not golden.
Finally we will make medallions with the sirloin of about three fingers of thickness, add the salt and brown them in a frying pan with the strong fire and some extra virgin olive oil.