Step 2:
place mince, onion, garlic, gherkin, tomato sauce and egg in a large bowl. Season with salt and pepper. Mix to combine. Roll 2 heaped tablespoons of mixture to make 8 balls. Flatten slightly. Place on a large plate. Cover with plastic wrap. Refrigerate for 30 minutes. Step 4:
heat a barbecue plate on medium-high heat. Cook patties for 3 to 4 minutes each side or until cooked through. Step 6:
meanwhile, preheat grill on medium. Cut each bun in half horizontally. Place halves, cut-side up, on a baking tray. Place patties on bottom half of buns. Top with one piece of cheese. Cook for 2 to 3 minutes or until buns are golden and cheese has melted. Step 8:
top mince patties with tomato sauce and american mustard. Sandwich with bun tops. Serve. 