1 Fry the bacon in 1 tsp oil until crispy, then drain on kitchen paper.
2 Peel and dice the avocado, and drizzle immediately with lemon juice to prevent colouring.
3 Put the garlic, yoghurt, mustard, vinegar and the remaining oil in a tall jug or beaker and blend to a creamy consistency. Season to taste with salt, ground black pepper and a pinch of sugar.
4 For the burgers, add a little salt and ground black pepper to the meat and knead in well. Shape into 4 patties. Oil the grill or barbecue and cook the burgers with a high heat for around 4 minutes on each side.
5 Slice the buns in half and put a burger on each bottom half. Spread with ketchup and mustard and top with the bun lid. Arrange the salad ingredients on plates. Break the bacon into pieces and sprinkle over the salad.
6 Drizzle the dressing over the salad and serve with the hamburgers.