- 1 large sweet white onion, sliced into 1cm/½in rings
- 1 litre/1¾ pints buttermilk
- 175g/6oz plain flour, sifted
- 50g/2oz polenta
- 1½ tbsp sea salt
- freshly ground black pepper
- 1 tbsp chilli powder
- vegetable oil, for deep frying
- balsamic vinegar, to serve
- 600g/1lb 5oz steak mince
- salt and freshly ground black pepper
- 50ml/2fl oz olive oil
- 4 x onion focaccia buns, sliced, griddled until slightly charred
- ready-made mayonnaise, to taste
- 1 large beefsteak tomato, sliced
- 2 large gherkins, sliced
- handful rocket leaves
- For the onion rings, heat the vegetable oil in a deep, heavy-bottomed pan until a bread crumb sizzles and turns brown when dropped into it. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
- Place the separated rings of sliced onion into a large bowl with the buttermilk to soak for 30 minutes, stirring occasionally.
- Place the flour, polenta, salt, freshly ground black pepper and chilli powder into a clean bowl and mix well. Transfer the mixture to a large plate.
- Take individual onion rings from the buttermilk, making sure there's lots of buttermilk clinging to the onion.
- Dredge each ring in the flour and polenta mixture and set aside, taking care not to shake off any excess flour and polenta coating.
- Carefully add the coated rings to the hot oil in batches of six and fry, stirring occasionally, for 3-4 minutes, or until crisp and golden. (The rings may sink to the bottom at first, but will then float to the top as they cook.)
- Carefully remove the rings with a slotted spoon and drain on kitchen paper. Repeat the deep-frying process until all of the onion rings are cooked.
- For the burger, place the mince into a bowl and season well with salt and freshly ground black pepper.
- Divide the mince into four and mould each piece into a patty shape.
- Brush each patty with the olive oil and place onto a hot griddle pan. Cook for four minutes on each side, or until completely cooked through.
- Place a burger inside each focaccia bun. Spoon over mayonnaise, to taste, and garnish with lettuce, tomato and gherkins.
- To serve, place the onion rings into a large bowl and sprinkle with salt. Place a small bowl of balsamic vinegar alongside to dip into.
- Place the burgers and buns onto plates and serve with the onion rings.