- 1 red onion
- 200ml/7fl oz red wine vinegar
- 80g/3oz caster sugar
- 600g/lb 5oz topside beef, minced (your butcher can do this)
- salt and freshly ground black pepper
- 4 fresh white rolls
- 100g/3½oz sliced gherkin
- 8 slices cooked streaky bacon
- 1 Little Gem lettuce
- 2 free-range egg yolks
- 100ml/3½fl oz vegetable oil
- 25ml/1fl oz white wine vinegar
- 1 tbsp wholegrain mustard
- 800g/1lb 12oz Maris Piper potatoes, peeled and cut into chunky chips
- vegetable oil, for deep fat frying
- 1 bunch of rosemary
- sea salt
- For the burgers, thinly slice the red onion and place in a bowl with the red wine vinegar and sugar. Set aside to pickle while you make the burger.
- Season the mince to your taste with sea salt and pepper and shape into 150g/5½oz patties using your hands. Set aside.
- For the mustard mayonnaise, separate the egg yolks into a bowl and gradually stir in the oil until creamy in consistency, whisking all the time.
- Stir in the wholegrain mustard and vinegar, season, to taste and refrigerate.
- For the chips, heat the vegetable oil in a deep fat fryer to 130C/275F (CAUTION: hot oil can be dangerous. Do not leave unattended.)
- Deep fry the rosemary for 30 seconds, remove with a slotted spoon and drain on a plate lined with kitchen paper. Chop the rosemary finely, mix it with the sea salt and leave to one side.
- Peel and cut the potatoes into chunky chips, place on a tray and steam for 15 minutes.
- Deep fry the chips for 3-4 minutes at 130C/275F. Remove with a slotted spoon and drain on a plate lined with kitchen paper.
- Increase the heat of the oil to 180C/350F and fry again until crisp. Remove with a slotted spoon, drain on kitchen paper and then toss the chips in the chopped rosemary and salt, to taste.
- Preheat a grill to hot. Cook the burgers for 4-5 minutes each side under the grill.
- Layer the burger on the roll with gherkin, bacon and reserved onion. Serve with the hot rosemary-salted chips and mustard mayonnaise.