This marinade works best on beef, but would also be tasty on pork.
1 cup strong brewed coffee
1/2 medium onion, chunked
1/4 cup Chinese black vinegar (See Note)
3 tablespoons packed dark brown sugar
2 tablespoons soy sauce
2 cloves peeled garlic
1/2 teaspoon ground cinnamon
1/2 teaspoon ground ginger (the powdered kind)
1/4 teaspoon ground cloves
1/4 teaspoon crushed red pepper flakes or to taste
1 (2 to 3 pound) beef "London Broil," flank or top round steak
Combine all ingredients except beef in blender or food processor. Blend or process until onion and garlic are pureed.
Lightly score beef steak on both sides in a criss-cross pattern (this helps the marinade permeate more deeply). Marinate steak with coffee mixture at least 8 hours or overnight, turning occasionally.
Chinese black vinegar has its own unique smoky flavor. Look for it in Asian markets. Or, substitute other vinegar. A 50-50 mix of balsamic and red wine vinegars work well.
Makes about 1-1/2 cups marinade