Season beef to taste and mix well with hands to combine. Shape into 1cm-thick, 5cm-diameter patties (use a 5cm-diameter cutter as a guide) and refrigerate until required. Bring to room temperature before cooking.
Heat a large frying pan (or barbecue) over medium-high heat. Cook patties in batches until browned on base (1-1½ minutes), turn and top each with Gruyère. Cook until cheese begins to melt (1 minute). Set aside to rest for 2 minutes in a warm place.
Meanwhile, preheat grill to high. Toast cut-sides of buns in batches (1-2 minutes), then top each bun base with a patty, cheese-side up, a slice of pickle, a squeeze of tomato sauce, sandwich with bun top and serve hot.
This recipe is from the April 2013 issue of Australian Gourmet Traveller.