Place the steaks between sheets of wax paper, then pound until each steak is about ½ inch thick.
Place the pounded steaks in a zip lock plastic bag. Add the mustard, cumin, 3 garlic cloves, cilantro, salt and pepper.
Refrigerate for 1 hour or overnight. Be sure the steaks are evenly covered.
In a large skillet, heat the oil over medium heat. Add the sliced onions and cook for about 3 minutes. Add the steaks into the skillet and cook for 3 minutes per side. Add the hogao sauce, cover and cook for 7 minutes more.