The first thing we are going to do is cut the sirloin into large medallions, which we are going to seal in the pan. Better to cut wide medallions, about three centimeters, because the sirloin is done very quickly and that way the meat will be juicier. Cook them over high heat on each side in a large skillet with a little oil. When they are well done on both sides, we reserve them.
In that same pan, lower the heat and cook an onion and two finely chopped cloves of garlic. Let it cook until the onion is translucent. We then add a glass of Pedro Ximénez (about 200 ml). Some people also add raisins, but the PX already tastes like raisins and is very sweet. In my opinion, they are excessive.
Let the wine cook over high heat for about two minutes, so that the alcohol evaporates, then add a tablespoon of refined corn flour (cornstarch) and another glass of chicken broth. Let the sauce reduce for about 10 minutes. At this point I prefer to pass the sauce through a blender, so that all the flavors are integrated and it is finer. We beat it well, we return it to the pan and, now yes, we integrate the sirloin medallions. We cook everything together for 4 minutes, so that the medallions are finished making and all the flavors are integrated.
This dish can be served immediately, but it is also delicious if we prepare it in advance.