Beefsteak with balsamic vinegar

Directions

• 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.