Separate a small piece of butter, set aside, heat the rest of the oil in a deep frying pan along with olive oil.

Put the steaks in the pan and fry them on both sides on high heat for several minutes.

Salt and pepper. Put on a dish. Do not let cool.

In the meat juice remaining in the pan, add the remnants of butter, onions and fry.

Wait until frying thickens, pour in balsamic vinegar and mix well.

Remove the pan from the heat and pour the hot sauce over the steaks.