Sandwich Steak

Bahan-bahan (4 porsi)

• 3/4 cup mayonnaise (, preferably whole egg)
• 1 large garlic clove (, minced)
• 3 large onions (, peeled and finely sliced (brown, white or yellow))
• 40 g / 3 tbsp butter
• 2 tbsp brown sugar
• 1 tbsp balsamic vinegar
• 1/4 tsp salt & pepper
• 600 - 700 g / 1.2 - 1.4 lb grilling beef steak ((Note 3))
• Salt and pepper
• 1 tbsp vegetable oil
• 2 tomatoes (, thickly sliced)
• 60 g / 2 oz rocket /arugula or other lettuce of choice
• Mustard ((I use American))
• Turkish bread (, about 60cm / 2 feet long (or 4 rolls / buns of choice))