1/4 cup soy sauce
1 1/2 cups water
2 tablespoons Worcestershire sauce
1/2 teaspoon salt
1/2 teaspoon minced garlic
1 teaspoon red pepper flakes
1 tablespoon sesame seeds
1 tablespoon rice vinegar
1 tablespoon vegetable oil
1 tablespoon vegetable oil
In a medium saucepan, heat soy sauce and water over medium heat for about 10 minutes, stirring frequently. Stir in Worcestershire sauce, salt, garlic, red pepper flakes and sesame seeds. Bring mixture to a boil, stirring occasionally, until thickened. Reduce heat to low, stirring occasionally, and cook about 20 minutes, stirring occasionally. Let stand about 15 minutes before carving.
Heat oil in a large pot over medium heat. Stir in vegetable oil and stir to dissolve. Add rice vinegar and pot over medium heat. Stir well and place steaks over oil, browning on both sides. Cover and simmer about 5 minutes. Remove steaks from oil and pour over steaks in pot.
Return steaks to pot, browning thoroughly on both sides. Place steaks over pot and add vinegar and rice vinegar. Bring to a boil, stirring occasionally, and cook about 9 to 10 minutes more, or until steaks are medium rare. Serve steaks with sliced green onions.