Place mince, oil, Worcestershire sauce, stock cube, salt and pepper in a large bowl. Using your hands, gently mix until combined. Divide into eight pieces and shape each
piece into a ball. Cover and refrigerate while you cook the onion.
Melt butter in a medium frying pan on medium heat. Sauté onion until just tender (3-4 minutes). Stir in vinegar and sugar. Cook, stirring occasionally, for a further 10 minutes,
until onion is sticky and caramelised. Remove from heat and season with salt and pepper to taste.
Heat a large frying pan on medium-high. Working in batches if needed, place burger portions in pan and smash flat with a spatula or potato masher (add a piece of baking
paper in between the patty and the masher). Cook for about 2 minutes, until edges are browned. Flip and place a slice of cheese on top of each patty. Cook until cheese
melts and patties are cooked through (about 1 minute). Remove from heat.
Cut Freya’s Brioche Style Buns in half and toast in a frying pan on high heat. Spread each half with burger sauce. Top the bottom halves of the buns with caramelised onions, lettuce, tomato, two cheese-topped burger patties and thinly sliced gherkins. Sandwich together with the top halves of the buns. Insert whole gherkins onto skewers and press into the tops of the burgers. Serve immediately.
• Can’t manage a double patty burger? The ingredients for the patties can be halved.