Caramelized Onion Steak Sandwich

Name: Caramelized Onion Steak Sandwich
Prep time: 15 min
Cook time: 25 min
Total time: 40 min
Cuisine: Canadian
Ingredients: 1 teaspoon oil (I use flavoured "Chili Oil"); 1 large sweet onion, thinly sliced (Walla Walla type); 2 garlic cloves, smashed; 1/8 teaspoon cayenne pepper; 1 teaspoon Worcestershire sauce; 2 tablespoons oyster sauce; 2 tablespoons balsamic vinegar; 12 -16 ounces sirloin tip steaks or 12 -16 ounces flank steaks; 1/4 cup beef stock or 1/4 cup red wine; 4 slices of your favourite thick toasted bread