1. Put the minced meat in a bowl and gently mix together,dividing into four patties. Move each patty from hand to hand for two minutes,making sure it is firm but not overworked,then shape into a ball. Gently flatten to form 2cm-thick patties and refrigerate.
2. Take patties out of the fridge about two hours in advance to allow them to be close to room temperature when you cook them. This will ensure an even temperature for cooking.
3. Heat a heavy-based frying pan large enough to fit all four patties until very hot. Brush olive oil over the patties and season liberally with sea salt. Cook on one side until a really good crust forms,then turn over to finish the cooking,adding two slices of cheese to each patty so it starts to melt. If you like the burger rare,cook for five minutes on each side;for medium rare,six minutes on each side;and for well done,seven to eight minutes on each side.
4. Remove the patties from the pan and rest for five minutes while you cook the bacon until it's reasonably crispy,but not dry.
5. To assemble the burgers,toast the buns under a grill on the cut side. Place the bun bottoms on four plates,and spread each with mustard. Place a slice of cheese over the mustard,then a rested patty with the melted cheese on top. Add bacon and top with lots of barbecue sauce,a dollop of mayonnaise and a few slices of pickled cucumber. Add a grind of fresh pepper,top with the bun lid and serve.