Mix the balsamic and salt, add the cucumber, cover and set aside.
Slowly fry the diced bacon in a non-stick frying pan until crispy, without adding any oil. Add the sugar and caramelize while stirring. Add the shallots and cook for approx. 4 mins. until soft. Pour in the wine and reduce almost completely.
Combine the sour single cream, chives, salt and pepper.
Mix the mince with all the ingredients up to and including the pepper, knead well by hand until the ingredients have combined to form a compact mass. Shape the mixture into 4 equal-sized burgers, flatten a little.
Charcoal/gas/electric grill: Cover and grill the burgers over/on a medium heat (approx. 180 °C for approx. 6 mins. on each side. Grill the buns alongside for approx. 2 mins., turning once.
Spread the chive sauce over the bases and tops of the buns.
Place the burger, bacon, reserved cucumber and lettuce onto the bottom half of the bun, cover with the top half of the bun.